of the conversion of the germinating spore into a single row of cells, one of which cells, by repeated divisions in all three directions of space, becomes the rudiment of the leafy axis. This phenomenon is as well marked as in any of the mosses. The outward form of the antheridia and archegonia in the two groups differs very slightly. The first stages of development of the fruit-rudiment of the mosses on the one hand and the Jungermanniæ on the other, are, it is true, very different. In the former the longitudinal growth is caused by the continually repeated division of a single conical apical cell of the organ, by means of septa inclined alternately in two directions; in the latter this growth is caused by the repeated division by horizontal septa, of four cells constituting the upper end of the fruit-rudiment. But the normal mode of cell-multiplication in the fruit-rudiment of the Marchantier (including the Targionies), and of the Riccies, coincides exactly with that of the mosses. Lastly, Anthoceros exhibits a form of cell-multiplication of the endogonium which is the same as that of the punctum vegetationis of the ends of the axes of a great number (probably the majority) of phænogams. The septa produced in the one apical cell of the organ, are inclined in regular succession towards the four points of the compass. The presence or absence of a columella, or of elaters in the ripe fruit, are points of no characteristic value; Anthoceros has the columella, but this genus and the Riccies have no elaters. Radula in the Jungermannieæ has a vaginula, and so has Anthoceros.

Upon instituting a closer comparison between the mode of development of different forms, four types soon become conspicuous, around which all the phenomena hitherto sufficiently investigated may be conveniently arranged. We thus arrive at the following equivalent groups, which are not however equally rich in the number of genera and forms. 1. Mosses according to the ordinary limits of the family, including the Sphagnaceæ.

2. Jungermannies; in which the leafy ones are connected with the leafless ones by a succession of intermediate stages.

3. Marchantieæ, Targionieæ, and Riccies; all intimately connected with one another by the similarity of the earliest conditions of the fruit, as well as by many vegetative phenomena.*

4. Anthocerotex.

The mode in which the second generation originates from the first is much more various in the vascular cryptogams than in the others. All ferns however agree in the fact that the first axis of their embryo has only a very limited longitudinal development; it is an axis of the second order which breaks through the prothallium and becomes the principal axis; and they all agree further in this, that the end of the axis of the first order never forms the root. All vascular cryptogams are without main roots; they have only adventitious ones.

In more than one respect the formation of the embryo of the Coniferæ is intermediate between the higher crytogams and the phænogams. Like the primary mother-cell of the spores of the Rhizocarpeæ and Sellaginella the embryo-sac is one of the axile cells of the shoot, which in the one case becomes converted into the sporangium, in the other into the ovule. In the Conifere also the embryo-sac soon becomes free from any mechanical connexion with the surrounding cellular tissue. The filling of the embryo-sac by the endosperm may be compared with the production of

* As, for instance, the precisely similar succession of the shoots; the separation of the tissue of the shoots into an upper layer with intercelluIar cavities, and a lower layer without cavities; the occurrence of peculiar thickenings upon the inner wall of the capillary roots, &c.

the prothallium of the Rhizocarpeæ and Selaginelle. The structure of the corpuscula bears the most striking resemblance to that of the archegonia of the Salviniæ, and still more of the Selaginella. Irrespective of the different mode of impregnation-which in the Rhizocarpeæ and Selaginellæ takes place by free spermatozoa, and in the Conifere by a pollentube, in the interior of which spermatozoa are probably formed-the transformation of the germinal vesicle into the primary mother-cell of the new plant in the Coniferæ and the vascular cryptogams, only differs in the fact, that in the latter there is usually one single germinal vesicle only, whilst in the former there are very numerous germinal vesicles, of which, normally, one only is impregnated. The embryo-sac of the Coniferæ may be looked upon as a spore remaining enclosed in its sporangium; the prothallium which it forms does not come to the light. In order to reach the archegonia of this prothallium the impregnative matter must make itself a passage through the tissue of the sporangium.

Moreover, the development of the pollen of the Coniferæ, when dispersed, varies in a marked manner from that of phænogams, and exhibits vital phenomena similar to those met with in the microspores of Pilularia, Salvinia, and Isoetes. The extinction of its sexual function (the protrusion of the pollen-tube) is preceded by a cell-formation in its interior, of which no instance is to be found amongst monocotyledons and dicotyledons.

Two of the phenomena which have led me to compare the embryo-sac of the Conifere with the large spores of the higher cryptogams, is common to the embryo-sac of phænogams, viz., the origin of the ovule from an axile cell, and the want of connexion with the adjoining cellular tissue. This is very remarkable in the Rhinanthaceae on account of the independent growth of the embryo-sac. The Coniferæ are closely allied to the phænogams in the fact that their pollen-grains develope tubes.

The phænogams therefore form the upper terminal link of a series, the members of which are the Conifera and Cycadeæ, the vascular cryptogams, the Muscineæ, and the Characeæ. These members exhibit a continually more extensive and more independent vegetative existence in proportion to the gradually descending rank of the generation preceding impregnation, which generation is developed from reproductive cells cast off from the organism itself. The closing members of this series, the Characeæ, pass through their entire vegetative development in this generation, whilst the vital phenomena of the generation which follows impregnation are limited to the filling with oil and starch of the newlyformed cell in the central cell of the fruit-branch or archegonium. The development of the latter generation in the Muscineæ is far more important, although in some instances, as for example in Riccia, it is very limited in comparison with the first generation, that, namely, which precedes impregnation. This state of things is reversed in the Ferns, the Equiseta, and the Ophioglosseæ. From the Characes up to these orders, there is an uncertainty in the different species as to the sexual function of the reproductive cells which are cast off from the organism itself, viz.,

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* Anthoceros-which in the development of the second generation stands very low in the scale-exhibits a remarkable analogy with the Characea, in the fact that, as in the latter, the formation of its antheridia commences by the growing out of the cells of the wall of an intercellular cavity. The well-known red globules of Chara are manifestly states of antheridia. Cavities communicating with one another are formed round the middle point of the hitherto solid globular mass of cells, within which cavities the antheridia-or cellular threads in whose joints the vesicles which produce the spermatozoa are formed-become developed.

the spores. In these orders species nearly allied to one another are Certain species amongst the partly monoecious and partly dioecious. Charæ, Muscineæ, the Ferns, and the Equiseta,* produce both kinds of sexual organs, archegonia and antheridia, upon the same individual of the generation preceding impregnation: the latter are always produced before the former. In other Characeæ, Muscineæ, and Equiseta, the male and female sexual organs are distributed upon different individuals a separation which is very complete in certain species of mosses, and not in others. The spores from which, in the Characeæ, Muscineæ, and Equiseta, diæcious prothallia are developed, exhibit no indication of the sex of the individual to be produced from them. But there is often a marked difference in the complete form between the male and female individuals: the former are much smaller than the latter; they are dwarfish. Extreme instances of this are to found, amongst mosses, in Dicranum undulatum and Hypnum lutescens. In the Equiseta also the male prothallia are always smaller than the females.

Lastly, the reproductive cells of the Rhizocarpeæ, Isoetes, and Selaginella exhibit, according to their sex, the most remarkable differences in their mode of development, size, and form, so long as they continue in vital connexion with the organism belonging to the generation following impregnation. In the Conifere the reproductive cells differ in their origin and formation but little from those of phænogams; they differ only in the nature of the vegetative growth subsequent to their formation -which growth in the Coniferæ is in a high degree independent-in the formation of the row of cells in the interior of the pollen-grain, as well as in the formation of the endosperm, and of the corpuscula in the interior of the embryo-sac.

There are so many essential points of agreement between the Coniferæ and the phænogams, that it is more to the point to get rid of the marked differences in their respective processes of embryo-formation, than to indicate in what they agree. One of these differences is the cell-formation inside the pollen-grain, but the principal one is the development of the endosperm and of the corpuscula, a process exactly analogous to the formation of the prothallia and archegonia of the vascular cryptogams, and which is entirely wanting in the phænogams. The whole series of developmental processes which occur in the Coniferæ between the filling of the embryo-sac with the cellular tissue of the endosperm and the production of the germinal vesicles in the corpuscula, is entirely passed over in the phænogams. Here the germinal vesicles are formed immediately in the embryo-sac. In the phænogams there is no vital phenomenon analogous to the development of the prothallia and of the endosperm of gymnosperns, just as in the cryptogams and the Coniferæ there is no analogue to the endosperm-formation which takes place in so many phænogams after the arrival of the impregnating organ at the embryo-sac. The breaking up of the pro-embryo of the Coniferæ into a number of independent suspensors is a phenomenon of the most peculiar kind, to which nothing amongst the vascular plants bears any resemblance,† and to which the division of the spore (i. e., the mother-cell of the oospores) of

The greater number of the Charæ and Muscineæ, a few only of the Equiseta, and all the known forms of Ferns and Ophioglosseæ.

†The formation of the pro-embryo of Loranthus Europeus out of four longitudinal rows of cells may be looked upon as a slight indication of this. One only of these cells, the terminal cell, becomes transformed into an embryonic globule. (Hoffmeister, in Abh. Kön. Sächs. Ges. d. Wiss.,' vi, 543.)

Fucus into several cells capable of impregnation and development* is hardly analogous, inasmuch as with the latter process the impregnation of the free spore commences and forthwith terminates.

The Microscope and its Revelations. By WILLIAM B. CARPENTER, M.D. Third Edition. London: Churchill. THIS work, which has now reached its third edition, needs no commendation from us. It is undoubtedly the best manual on the use of the microscope in the English language. Nevertheless, this edition contains a large mass of new matter which claims our recognition. The classification of the Diatomaceæ has been remodelled in accordance with the views of Mr. Ralfs, and the account of that group has been considerably extended. The account of the Rhizopoda has been altogether rewritten, and that of the Infusoria has been augmented by a summary of Balbiani's recent researches on their sexual reproduction. As might be expected from the extent of the author's own researches on Foraminifera, the chapter on these organisms has been rewritten and greatly extended. Mr. Salter's researches on the teeth of Echinus, and those of Mr. Houghton on the parasitic habits of the larva of Anodon, have been embodied with the author's more recent views of the structure of the shell in the chapter devoted to the Mollusca. Additions have been made also to the account of the forms of Annelida, and the description of the structure of the shells of the Crustacea have been considerably modified. In the section devoted to Insects, Dr. Hicks' researches upon their eyes, and Mr. Beck's upon the Podura scale have been described. Amongst the new accounts of structure among the vertebrate animals, are those of Mr. Whitney on the circulation in the Tadpole. Mr. Rainey's important researches in "Molecular Coalescence" are also noticed in this edition. The work is still further improved by the addition of ten separate plates, and twenty woodcuts. Two of the plates, representing chiefly the circular forms of Diatomaceæ, are on steel, and form frontispieces to the work. It gives us much pleasure to recognise, in so large a quantity of the new matter which Dr. Carpenter has introduced into the present edition of his work, the results of researches which the Quarterly Journal of Microscopical Science' has been the means of introducing to public notice. We feel that the study of this work will be one of the best incentives to the student of the microscope to pursue his investigations in a spirit which will enable him to become a contributor to our pages, and a future helper of Dr. Carpenter in the subsequent editions of his work.

* Thuret, 'Ann. d. Sc. Nat.,' iv Sér., 1854, p. 273.

NOTES AND CORRESPONDENCE.

Note respecting Parasites found in the Blood of the edible Turtle.-In Vol. i, N. S., of this Journal, p. 40, is an account by Mr. Canton, of some fusiform ova, found by him adhering to the eyes of the edible turtle. Similar organisms have since been noticed by Dr. Leared, in the blood from the heart of the same animal, in two instances. In one of these latter cases, examined in August, 1860, the heart also contained numerous minute fluke-worms, which were pronounced by Dr. Cobbold to belong to an undescribed species of Distoma, and named D. constrictum, from its peculiar form. Whether the minute oviform bodies noticed by Mr. Canton, and these Distomata stand in any relation to each other is yet to be made out, and is an interesting subject for enquiry. Dr. Leared's account of the Distomata and oviform bodies will be found in vol. xiii. of the 'Transactions' of the Patho. logical Society, p. 271.

On the Terms used in the description of Diatoms.-Dr. G. Fresenius, in the 'Senckenb. Proc.' vol. iv., p. 63, describes and figures four species of Navicula, one being new. Pinnularia Silesiaca, Bleisch, and Amphora selina, W. Smith. In his introductory remarks he proposes the adoption of the terms, "frons" and "latus," to express what English observers call the "front view" and " side view." (N. Hist. Rev.,' vol. ii., No. 8, p. 481.)

On the occurrence of Parasitic Sacs on Crustacea and some Insect-Larvæ.-Lieberkühn (Mull. Arch.,' 1856, p. 494) and Schenk (Verh. der Phys.-Med. Gesells,' in Würzburg, 1858) have described certain organisms parasitic upon the gills of the larvæ of Phryganea, Asellus aquaticus, and Gammarus pulex. These organisms have been since examined by Professor Cienkowski, who considers them to be forms of a uni