by Mr. Blake under the "Conici," diverging from this and more restricted in time, having variously shaped apertures, and singularly inflated, fusiform, pyriform, or flask-shaped shells, are the genera Phragmoceras, Gomphoceras, Poterioceras, and Ascoceras, and placed under the group "Inflati" by the author. The other two groups of the Nautiloidea-the Spirales and the Irregulares possess so great a shell curvature that they assume the form of whorls, which may or may not be in contact. This fact appears of sufficient importance to justify Mr. Blake in regarding it as the basis for establishing the group "Spirales," in which is placed the genera Nautilus, Gyroceras, Trochilites, and Clymenia, &c., finally through peculiarity of form, such as want of symmetry, or loss of, or changes in curvature, are many of peculiar aspect, which Mr. Blake places under the group "Irregulares," the genera contained in which are Trochoceras, Lituites, Ophidioceras, and Cryptoceras. These researches have led to the construction of the table of classification above given.

Prof. Blake commences his systematic description of the species with the genus Orthoceras. No less than 70 species in this genus are described by the author, ranging from the Tremadoc rocks to the uppermost Ludlow beds (the Tile-stones). The species mostly abound in the Bala beds, the Wenlock shales, and the two Ludlows. The literature or bibliography of the species of the Orthocerata, their descriptions, and that of the 5 sub-genera is of the greatest value, and an addition to our knowledge of this oldest known genus in the British rocks; Cyrtoceras being its only associate in the Tremadoc beds. The sub-divisions of the genus by Quenstedt, M'Coy, De Koninck, and Barrande are given. Mr. Blake adopts Barrande's views and grouping of the Orthocerata into two groups: (1) the Brevicones; and (2) the Longicones. The latter, which is very numerously represented, Mr. Blake divides into the Annulati, the Angulati, the Lineati, the Imbricati, and lastly the group Leves. In this latter group is temporarily placed all species whose external surface is unknown. Then follows concise but clear descriptions of the five sub-genera-Actinoceras, Endoceras, Tretoceras, Conoceras, and Gonioceras. For the first time we now have the 70 British species of Orthocerata brought together, and most ably described and figured; 3 species belong to the group "Brevicones," and 67 to the group "Longicones." Of these, 20 species fall under the group Annulati, 6 under the Angulati, 13 under the Lineati, 7 under Imbricati, and 22 in the group Leves. We are now able to investigate all the known species of this extensive Palæozoic genus, and no student need be at a loss to determine, either through original description and drawing, or the reproduction of type species, any forms that he may meet with in the Silurian rocks of the British Islands. The author's plan of first describing in every instance the type of the species, is of extreme value, as it at once (if a known species) clears up its history; this with reference to the original figure and description by the author, and its reproduction in the monograph, ensures and affords every chance of right determination. Following the "type" is the general description, then its relation to other known forms, British or foreign, followed by its distribution in time or space; this plan is implicitly followed throughout the entire

volume-it is clear, definite, and systematic. The next important group described by Mr. Blake are the Cyrtoceri, numbering 22 species. These curved Cyrtoceri Deshayes termed Campulites, restricting the term to those species having the siphuncle on the inner side. Goldfuss, however, regardless of the position of this organ, named them Cyrtoceras; Billings, De Koninck, Sandberger, Giebel, and Barrande have all proposed divisions for the classification of Cyrtoceras. Blake follows Barrande, who divides them into two series, according to the position of the siphuncle: (1) the Exogastric, in which that organ is external; and (2) Endogastric, in which it is internal. Prof. Blake proposes a third grouping for these species, in which the siphuncle is near the centre, calling it "Mediogastric." The Bala, Wenlock, and Lower Ludlow beds contain most species of Cyrtoceri. The species C. precox, from the Tremadoc beds of Garth, in North Wales, and from Llanerch in Pembrokeshire, with Orthoceras sericeum are probably the oldest forms known.

The singular genus Gomphoceras receives much careful analysis from Prof. Blake. Six of the 11 species are new, and there appears to be good reason for their establishment; with one exception the species are all (10) Upper Silurian, 8 of the 11 are in the Lower Ludlow beds, and 5 in the Wenlock Limestone. Two quarto plates are devoted to this remarkable genus. Four of the 7 species of Sowerby's genus Phragmoceras are also new, and for the first time figured. Like Gomphoceras this genus is chiefly Upper Silurian, the Wenlock and Ludlow strata being characterised by them. Mr. Blake adds much to our knowledge respecting the species of the genus Ascoceras of Barrande, hitherto little known or understood; the species in Britain are confined to the Ludlow rocks.

The group Spirales, illustrated by the genus Nautilus and its sub-genera, receives ample and critical notice, and shows how varied have been the views of naturalists upon the affinities of this old genus, established by Breynius in 1732. The value of the sub-genera in this as in all the large groups is of much significance in tracing the history of the obscure forms classed under the genus Nautilus or Nautiloid remains in the Lower Paleozoic rocks. Five of the so-named genera-Trocholites, Clymenia, Aturia, Discites, and Nothoceras are placed under the genus Nautilus as sub-genera. Mr. Blake gives Quenstedt's, D'Orbigny's, and De Koninck's classification or sub-divisions, and suggests one of his own. Quenstedt proposed to subdivide the genus Nautilus into 8 groups: (1) the Insecta, (2) Clymenia simplices, (3) Clymenia angulosa, (4) the Moniliferi, (5) Bisiphites, (6) Simplices, (7) Undulati, (8) Aganides.

This and the classification by De Koninck ("Terr. Carb. de Belg."), in which he partly follows Quenstedt, are the only two hitherto recognised divisions of the genus. The Belgian Professor places his Palæozoic species under the following six heads: (1) Imperfecte, (2) the Striati, (3) the Radiati, (4) Lævigati, (5) Clymeniœ simplices, and (6) Clymenia angulata; four of the six being those of Quenstedt. Prof. Blake proposes or suggests a simpler grouping. No. 1, Simplices, illustrated by the sub-genus Trocholites; 2, the Radiati, those species having radiating, sigmoidal, or angular ribs; 3, the Ornati, variously ornamented, chiefly Carboniferous,

equivalent to M'Coy's sub-genus Temnocheilus; 4, the Sinuosi, those with sinuous sutures; and 5, those species with nummuloid siphuncles (Trias only).

Probably only three species of Nautilus occur in the Silurian rocks-Nautilus quadrans, N. Holtianus, and N. Bohemicus. This last-named species appears to be the Lituites Biddulphi of Sowerby (1838); but his insufficient description, in the "Sil. Syst." of Murchison, prevents true identification. They are all three Upper Silurian forms. The Lower Silurian rocks of Newfoundland and Canada have yielded eleven species. In the Carboniferous strata Nautilus attains through Discites its maximum development. In the Permian only one species is British, and three American, and is now the only living representative of the Tetrabranchiata. The sub-genus Trocholites (three species are Lower Silurian. These six forms are the only true Nautiloidea in the Silurian rocks, The last group (4, the Irregulares) in Mr. Blake's classification receives three genera: Trochoceras, with 12 species; Lituites, 2; and Ophidioceras, 2 species. We have no representative of either the Endogastric or Exogastric group of Barraude in this country. American and Swedish Lower Silurian species are somewhat abundant, in Britain it is chiefly an Upper Silurian genus. Of the 12 species known 8 are Upper Silurian-Wenlock and Ludlow and the Llandilo, Bala, and Llandovery beds yield the remaining Trochoceri. Five of the 12 species are new to Britain, described and figured by Prof. Blake for the first time. The two type species-Trochoceras (Lituites) cornu-arietes (Sowerby), and Trochoceras (Lituites) giganteum (Sowerby)—are admirably refigured and described by Mr. Blake, the general descriptions adding to their specific value, and the determination of Bohemian forms of Lituites in Britain materially adds to the correlation of the two faunas. Barrande's genus Ophidioceras (Lituites, auct.) seems to have been recognised by Mr. Blake; it differs from typical Lituites by the whorls being accurately in contact. The Lituites articulatum, Sow., was long ago figured as Lituites in the "Sil. System," p. 622, t. 11, f. 5, and adopted by Salter. The straight ribbing and band distinguishes this genus from Lituites. This volume concludes with general observations, and highly suggestive many of them are. Prof. Blake endeavours to throw some light upon the laws which govern the appearance and disappearance of forms of life, and into the nature of those groups of individuals to which we assign the term species.

Mr. Blake prepares a table, condensed from the larger and preceding one on pp. 233-236. This condensed table shows the numerical value of the species occurring in the II genera, and ranging through the ten formations or horizons, thus showing their increment, decrement, and stratigraphical distribution. Both tables show three maxima in the Ludlow, Wenlock, and Bala beds-in the Ludlow 65 species, the Wenlock 43, and the Bala 39. Mr. Blake does not believe that there was a corresponding falling off between these epochs; he draws conclusions from the comparative fewness of species in the Wenlock Limestone as compared with the Ludlow shales above and Wenlock shales below that formation. Of the four groups given the Conici first appear, and constitute the bulk of the Lower Silurian fauna, 31 species occurring in the Bala rocks [the Tremadoc only yielding

two species, the Llandeilo 9, and the Lower Llandovery 8, or 19 for the three horizons]. The Conici and Spirales are the only two groups which continue on in time or range into the higher divisions of the Paleozoic rocks (the Devonian and Carboniferous), the Inflati being represented by Poterioceras, &c., in the Carboniferous series. Mr. Blake next considers the characters of the individual genera and their appearance in time, but somewhat begs the question to suit his particular view upon evo'ution; it surely can hardly be safe to speculate upon any particular curve or part of the curve in any particular genus, to argue for descent through evolution, other conditions not known. Neither Cyrtoceras precox or Orthoceras sericeum-which are the oldest species known in Britain -"are transitional forms, both being well characterised," and it is questionable whether the group which has been longest in existence in a given area, will there most abound, many physical conditions may tend to prevent that, "though we grant that possibly the greater the abundance of individuals, the greater is their chance of preservation in the rocks, the nature of the deposit admitted.

In the paragraph on p. 239, having reference to the genera Cyrtoceras, Phragmoceras, and Gomphoceras, more evidence is wanting before we can draw any conclusion as to priority of appearance, or show that those having the siphuncle internal (Endogastrica) appeared first or preceded the Exogastrica (with the siphuncle external); it is true we must take the evidence as it stands, or as we find it; it is, however, wiser not to theorise upon such slender materials.

Prof. Blake next notices and discusses the question of species (pp. 239-243), and has pronounced opinions upon this vexed, complicated, and philosophical question, naturally the old idea of the independence of species is rejected. Mr. Blake adopts all through his book the method of "actually describing a type-specimen around which the other forms designated by the same name may cluster." When the original type has not been seen or found, a type is selected to which others are compared. In attempting the explanation of the phenomenon of distinct species or specific groups, it is well known that two theories are now held: (1) that which considers each species a "special creation, though inexplicable"; or, (2) "that which asserts the development of one from the other by a process of evolution." Mr. Blake appeals to palæontology to show, through its researches, the gradations between one species and another. The result to Mr. Blake's investigation in this and other groups is against "fixity of species." He states, that "if species were such definite entities as they were once supposed to be, they ought to be much more easily distinguished than they are, and that the many variations of form which will be found included, and necessarily included under one specific title, whose 'general description' thereby becomes one of considerable latitude, show that different specimens are not so closely linked as that theory would imply." On the other hand, " Does this present study," asks Mr. Blake, “give any positive aid to the theory of evolution?" He fails to see any reasonable solution or answer. It is evident that among "the many forms which flourish in any one epoch, it must be impossible to say with certainty which was the descendant of any particular form in the preced

Mr. Blake selects certain species of Crthocerata which may have been produced by descent; at the least it is only supposition, and he states that there is no proof that they are actually so connected, but to the general theory of evolution--which merely states that every form of life has been developed from a preceding one nearly allied to it—the present study affords no contradiction or difficulty, but affords aid-which if not so great as could be desired, is yet as much as could be expected. In the present study of the Paleozoic Cephalopoda we have a fair representative of a successive fauna of the same class, and the species are grouped round a series of central types; and so long as the surrounding circumstances remain constant and the same, the process of evolution by indefinite variation and survival of the fittest should either be uniform, and leave relics having no special grouping, or it should cease when the best adaptation to the surrounding circumstances or conditions had been acquired. These views are expressed and carefully argued by Prof. Blake, in the concluding pages of his work. "The great defect," writes Mr. Blake, "of the theory of natural selection is that it leaves the original variation, which is the basis of the whole to chance; chance variations are not likely to lead to any law." "The part which it has effectually performed is to show how variations of the individual may produce permanent changes in the species, and thus break down the idea of the fixity and independence of the latter." "We are, perhaps," says the author, as yet too dazzled by the brilliancy of the theory to perceive its inadequacy as a complete account of life or to place it as one link only in the chain of explanations."

The O General Observations" of Prof. Blake on pp. 237-44 are a fitting termination to the laborious part undertaken by him in describing the 145 Silurian species. The work has been most carefully and honestly done, and now for the first time we possess a complete monograph upon the Tetrabranchiate Cephalopoda of the oldest Paleozoic rocks; no less than 31 quarto plates illustrate the species, and all are drawn life-size. Mr. Blake has examined 2000 well-characterised specimens, and has visited all the museums and private collections in Britain likely to contain materials for his work, and as he remarks, the work includes a description of every known specimen so far as it presents any available characters.

The fragmentary state of nine-tenths of the specimens collected, demanded from the author the most careful examination, whether by comparison or through description of specimens, and those who know the condition of Silurian Cephalopoda as occurring in this country will indeed appreciate the critical labour of Prof. Blake; he has rendered great service to palæontology. The book was the one want, as a completion to the works of Murchison, McCoy, Salter, and Sowerby in Britain; a companion to the grand monographs by Barrande upon the Cephalopoda of the Silurian Rocks of Bohemia, also a fitting accompaniment to the monograph by De Koninck upon the same group for the Silurian and Carboniferous Rocks of Belgium. No library devoted to natural science should be without this first volume, and no student of Paleozoic species can do without it. No group of invertebrata are of such importance to the stratigraphical

Palæozoic species number nearly 400, and in Bohemia the Silurian Cephalopoda, as described by Barrande, reach the great number of 1600, the Devonian species 500, and the Carboniferous species of Europe 350 species; these totals will at least give some idea of the life and distribution of this class of mollusca through time in Europe, and as Prof. Blake's first volume only treats of the Silurian of Britain, we wish him further success in his continued work upon the British Devonian and Carboniferous species, the fossil forms in which require the most minute, careful, and detailed study.

OUR BOOK SHELF

R. E.

Social History of the Races of Mankind. Fifth Division: Aramaans. By A. Featherman. (London: Trübner, 1881.)

WE do not like to discourage a student who has evidently a zeal for knowledge, and must have given great labour to compiling the comprehensive account of human society, of which this volume is the first instalment published. But we are bound to say he does not seem alive to the differences of value among the travellers' books of which he gives a list at the end of each section, and out of which he has pieced together extracts describing Jews, Arabs, Egyptians, &c. Thus some statement about the Copts may be out of Lane's "Modern Egyptians," or it may be out of Miss Lot's "Nights in the Harem," and the reader would rather like to know which is which. Mr. Featherman writes in his preface: "The facts have been selected with critical discernment, and no doubtful or incredible statements are admitted in the text, unless controverted in a footnote." Then follows an introduction, which begins: "The primæval man did not spring from a single stock, or from one ancestral type. He arose under varying conditions, and at different geological periods. The initiatory forces of nature which caused his primitive development, existed in the same degree in all the isothermal regions of the earth, and whenever the favourable circumstances were capable of producing and fostering into maturity the human animal, there he appeared," plain that the author's critical discernment does not &c. &c. Putting preface and introduction together, it is enable him to know a doubtful statement when he sees it, even when it is of his own making. In fact he does not quite know where he is, or a casual look into his volume would not show the ancient Egyptians classed among the Aramæan or Semitic nations without mention of their great physical difference from Jews and Arabs, nor would there be found in the account of the Egyptian religion a mention of Isis as being Ceres and Proserpine, mother and daughter at once. The book deserves a place on the library shelf, and will be useful to students, especially for its descriptions of Druses, Talmud Jews, and other littleknown minor groups. It is doubtful if its reception by the public will justify the series being continued; but in case it goes on, the materials ought to be more carefully selected, and references given.

Commercial Organic Analysis. By A. H. Allen. Vol. II. (London: Churchill, 1882.)

THE first volume of Mr. Allen's work treated of cyanogen compounds, alcohol derivatives, phenols and acids; in this second part the very useful and practical character of the work has been fully maintained in the description of the properties, tests and assay of the hydrocarbons, fixed oils, and fats, sugars, starch and its isomers, alkastated in his preface, all mention of dyes and colouring loids and organic bases, &c. The author has omitted, as matters, coal-gas, and animal products, on the ground that their consideration would have inconveniently in

creased the size of the work. This is somewhat to be regretted, as they are matters of quite as much importance as fixed oils, &c., to which a long chapter is devoted, and their inclusion would have certainly increased the value of the book for all general purposes.

The chapters on paraffins, terpines, and homologues of benzene are very clear, and in many cases detailed methods of assay, as, for instance, with benzene, anthracene, &c., are given that will be found of practical value. A large chapter is devoted to the description of methods of examination of fatty oils and fats employed in the soap manufacture, and the same section also gives considerable general information respecting varieties of soap with methods in some cases improved by the author, for the analysis of soaps; in particular a tabular arrangement of analysis of a soap on p. 242.

About 100 pages are devoted to the important subject of sugars, and in this space we find an admirable condensation of methods in use, both optical and chemical, for the detection and determination of the various varieties of sugars met with commercially. The optical portion is prefaced by some short remarks on construction, and varieties of polometers in use, which might with advantage have been somewhat extended.

All the methods given in this section are up to date, and cannot fail to be of use not only to the practical man, but to the student.

The chapter on the alkaloids is also a very complete compilation of methods of detection, &c., that have been proposed and found to be reliable up to date. No doubt the book will be found valuable as a reliable compilation of methods, &c., as such, saving much time and trouble in referring to the original publications. The author is an eminently practical chemist, and in his preface to the first volume seems to deride the teaching of "ultimate organic analysis" and the "ringing the changes on the everlasting-chloro-bromo and nitro derivatives of bodies of the aromatic series."

The quality of Mr. Allen's production atones somewhat for this ebullition, for his book requires a considerable amount of theoretical knowledge to be possessed by the user; and it is very desirable, if we are to maintain a position as chemists at all, that the cant about "purely practical work" should cease, and a more thorough foundation in theoretical chemistry be imparted to students, so that they may become reliable practical men, and not mere machines for manipulating test-tubes.

Nordenskjöld's Arctic Voyage Round Asia and Europe. A Popular Account of the North-East Passage of the Vega, 1878-80. By Lieut. A. Hovgaard. Translated from the Danish by H. L. Brækstad. Maps and Illustrations. (London: Sampson Low and Co., 1882.) LIEUT. HOVGAARD, of the Danish Navy, was one of the most efficient members of Baron Nordenskjöld's wellselected staff on board the Vega. When he returned from the remarkable voyage, he very naturally felt impelled to tell his countrymen how he had fared and what he had seen. This he has done in a pleasant and popular style, utilising to some extent the material collected by his chief. Lieut. Hovgaard, while dealing mainly with its lighter aspects, gives a fairly complete sketch of the voyage. The translation is well done, and the translator deserves special credit for the intellgible way in which he has rendered Russian names. The illustrations are not up to a very high mark.

The Sphygmograph; its History and Use as an Aid to Diagnosis in Ordinary Practice. By R. E. Dudgeon, M.Ď. 8vo., pp. 72. (London: Bailliére, Tyndall, and Cox).

THIS book may be of some service to beginners, as it gives rudimentary instruction in the use of the instrument, but this is all it does. The history is carelessly written,

the account of the indications given by the sphygmogram is imperfect, and the deductions drawn are sometimes, we think, incorrect. From a curve in the upstroke the author concludes that the ventricular contraction is of a peristaltic character, a conclusion which would be most important if it were correct. But he does not at all take into consideration the great probability that this curve is due to instrumental error, inasmuch as it does not appear in the tracings obtained by Marey's sphygmograph, in which the connection of the writing-lever with the artery is more perfect than in Dr. Dudgeon's instrument. The chief value of the book consists in the description and directions for applying Dr. Dudgeon's sphygmograph, which certainly possesses the great advantage over other instruments, that it is much cheaper, and can be applied much more quickly, and with much less trouble. A Great Mathematical Question. By T. Wakelin, B.A. (Melbourne: G. Robertson, 1881.)

A PAMPHLET of 16 pp., with a coloured diagram, the object of which is to show the fallacy of the measure of kinetic energy. It is an account of the old dispute originated by Leibnitz, and about seven pages are taken up with extracts from Whewell's "History of the Inductive Sciences" (vol. ii. pp. 68-70); Penny Cyclopædia, "Vis Viva"; Encycl. Brit., "Energy"; Balfour Stewart, "Heat" (pp. 301-4); and Routh's "Rigid Dynamics" (pp. 260, 263, 270-1), with a reference to Todhunter's "Mechanics" (pp. 210, 211). We would suggest, as additional references, Clerk Maxwell, "Matter and Motion" (§ lxxvii.), and Tait's "Recent Advances in Physical Science." Mr. Wakelin concludes: "It will therefore be seen that the distance through which a body falls during the time of falling, is not a measure of the work of the force of gravity during that time. This, of course, means that the ordinary measure of the kinetic energy of a mass in motion is an erroneous one.”

LETTERS TO THE EDITOR

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts. No notice is taken of anonymous communications. [The Editor urgently requests correspondents to keep their letters as short as possible. The pressure on his space is so great that it is impossible otherwise to ensure the appearance even of communications containing interesting and novel facts.] The Existence of a Voice in Lizards

THE letters on the existence of a voice in lizards, by M. Pascoe and S. P. Oliver, in NATURE, vol. xxv. pp. 32, 174, gave me much pleasure, being a confirmation of observations first made and published by myself in 1874, but doubted in different quarters. In my paper, "Zoologische Studien auf Capri, II. Lacerta muralis coerulea, ein Beitrag zur Darwinschen Lehre, Leipzig, Engelmann, 1874" (p. 20), I have laid down the result of my observations, in the first instance, concerning the habits of the bluish-black wall-lizard, Lacerta muralis cærulea, discovered by me on the Faraglione rock near Capri, and subsequently on those of other wall-lizards. There, I say: "To the harmlessness (or fearlessness, mentioned previously) of the blue inhabitant of rocks-Lacerta muralis cærulea-I owe the discovery of the animal's intonating capacity, a peculiarity generally ascribed among reptiles to the geckoes and chamæleons,

but never observed in wall-lizards till now."

One summer-day I heard in the room where I kept a cage of lizards a peculiar sound, similar to the piping of a nestling, only softer. Having listened attentively, I was surprised to find it proceeding from the throat of one of my male blue lizards. Leisurely resting on a stone, the animal repeated the sound a dozen times, perhaps at intervals of about a quarter of a minute, each time opening its mouth a little way. For several consecutive weeks I noticed the same kind of voice in other individuals of both sexes, after which period I did not hear it for months. A series of these calls were taken down by me from ear; I give them here: "chri, bschi, riä, bi, bschiä."