many, and since our knowledge of the phases of existence of a large number is so imperfect, it is really impossible to establish any satisfactory classification. On this account, and also to bring together for convenience sake, a mass of information respecting several collections of beings enumerated among the Anenterous Polygastrica of Ehrenberg, difficult or impossible to arrange under any other heading, we resort to this artificial division, and in so doing have the example of Perty and other writers." The collection of the observations and opinions of the most celebrated and trustworthy microscopists on these minute organisms is certainly of great value, and it is at least a con. siderable advantage to have doubtful and uncertain forms, most of which must now be considered as transient conditions of some of the lowest vegetables, whilst they are described so as to be recognized, and the materials for their study are brought together, carefully se. parated from beings whose animal character is generally admitted, and which are to be considered as members of the lowest sub-kingdom or branch of the animal kingdom. When we see the number of Ehrenberg's genera, and even families, which are now found to be only successive transformations of some of the lower Algae in the progress of their development, we cannot but acknowledge and rejoice in the bright light thrown upon so obscure a subject, affording the greatest encouragement to persevering labour and patient research.

The third section, Protozoa, is equal in extent to the two preceding, and contains a full and careful account of observations and opinions in relation to this great division of minute creatures. They are divided into the sub-sections Rhizopoda and Ciliata, which last division corresponds to Infusoria in the limited sense now given to it by many naturalists. In his general table, the author assigns their place among Rhizopoda to Polycystina, Thalassicollida, and Spongiada, of which groups-lest his subject matter should be too much extended-he has omitted any further notice. Respecting them, we will only suggest that whilst all that is known of them points out Polycystina as true Rhizopoda, the sponges (Porifera or Amorphozoa) appear to constitute a division of equal rank with Rhizopoda and Ciliata (Infusoria), whilst there are strong reasons for regarding Thalassicollida as only a sub-division of sponges.

In this slight indication of the nature of the contents of an extentensive and elaborate work, we must avoid minute criticism, ecpecially of views which are rather recorded than adopted by the authors. The

great merit of the work is as an abstract and summary of what has been done upon an extensive and most curious subject of inquiry, and in consequence of this merit, no worker with the microscope would willingly remain without it. The perfection of his means for observing minute objects is to little purpose if he cannot assign to them a position, and obtain some insight into what is known or believed of their nature and affinities, and he could scarcely find elsewhere any similar collection of the objects which may occur to his notice.

The fourth section is devoted to Rotatoria or Rotifera, the wheel animalcules, and contains a full and highly interesting account of their structure, mode of life, and the various plans proposed for their classification. The discussion respecting their affinities is given at some length. We have the arguments of Leydig to prove them to be a section of Crustacea; the reply of Vogt, maintaining their connection with Vermes; the speculation of Gosse, on their resemblance to insects, which we must regard as very fanciful; and the novel view of Huxley, according to which we are to place them with Annelida, Echinodermata, Trematoda, Turbellaria, and Nematoidea, as a group of the lower Annulosa, under the name of Annuloida. Believing that we are justified in maintaining Cuvier's sub-kingdoms of Articulata and Radiata, notwithstanding the great changes recently proposed, that on the one hand Coelenterata is entirely unnatural, and on the other hand the separation of the jointed-limbed from other articulated animals is unjustifiable, we agree both with Leydig and Vogt in considering the Rotifera as exhibiting an articulate structure, though of the lowest character, and we would settle the dispute as to whether they belong to Crustacea or Annulata, by making them a distinct class of the articulate sub-kingdom, which will thus contain: 1. Arachnida; 2. Insecta, of which Myriapoda is to be accounted a sub-class; 3. Crustacea, including Cirrhopoda; 4. Annulata, of which Entozoa constitute a sub-class; 5. Rotifera, which, as the lowest form of the articulate series, exhibit analogies with the lowest mollusca (Polyzoa) and with embryonic states of the higher Radiata as well as with Protozoa.

Another short section, the fifth, is devoted to the Tardigrada, which are, we think, rightly treated as a very low form of Arachnida. In all the classes of articulate animals, whilst a common type may, in our opinion, be well recognised, the range of development is very extensive and varied, so that animals of very low organisation appear

in the same class with others representing the highest development consistent with the type. The first comparison of a Mygale or a Scorpion with a Mite or a Tardigrade, would hardly suggest any affinity; but further study brings us acquainted with common characters, and leads us to view them as parts of a series in which amidst the greatest variety of development an uniform type of structure is observable.

The systematic history of the several tribes occupies about half the volume, and is invaluable to the practical microscopist, especially when it is considered that the descriptions of the objects are aided by forty closely filled plates, each containing on an average not less than fiftyfive subjects beautifully engraved. Such a collection of minute organisms admirably represented, as many times the cost of this work would not enable us to obtain elsewhere.

W. H.

TRANSLATIONS AND SELECTED ARTICLES.

EXPERIMENTS ON THE MIGRATION OF ENTOZOA.

BY MM. A. POUCHET AND VERRIER.

(Translated from the Comptes Rendus of May, 1862.)

MANY of our readers are acquainted with the modern views respecting the transformations of Entozoa, as taught by Van Beneden, Von Siebold, Küchenmeister, &c. The recent researches of two eminent French naturalists, MM. Pouchet and Verrier, creating some doubts on the subject, we copy a translation from the Comptes Rendus for May, 1862, giving an account of their experiments; and as we find that Van Beneden has replied, and these writers have attempted further to justify their views in the same publication, we shall continue the subject as the materials come to hand :—

"In a work published by one of us in 1859, a close comparative examination was made of the doctrines of those observers, who in Germany and Belgium had occupied themselves with the subject of

the metamorphoses of the Entozoa and their peregrination through the living organism. The obvious result of this examination was to excite very weighty doubts in every thoughtful mind. M. Davaine, in his remarkable Traité des Entozoaires, also says that the conclusion in his mind, from the agreement in the facts and the divergence in the opinions of the experimenters, was that the question still demands sound criticism and fresh researches.'

"One observer states that, on nine different occasions, he has succeeded in producing Taeniae in the intestine of the dog, by causing it to swallow some Caenuri of the sheep. It will be seen that we have also been as successful as this experimenter, and that, in fact, it is the great amount of this success that has given rise to our doubts-we have occasionally reaped more than we have sown.

"But before giving an account of our experiments, let us recal briefly what are the Entozoa upon which they have been instituted. The first is the Caenurus cerebralis, a vesicular, polycephalous worm, common in the sheep, in which its presence causes the disease termed 'staggers.' The second is Taenia serrata, a cestoid worm, extremely abundant in the dog.

According to the experiments above referred to, this is what takes place:-The dogs devour the heads of the diseased sheep, and the Caenuri are by this means introduced into their stomachs. Having reached this locality, each of the polycephalous helminths separates itself from the parent cyst, elongates enormously, and becomes a Taenia. The entozoon returns to the sheep in this wise: When the Taeniae of the dog have attained their full development, the rings which they throw off are passed with the excrement, fall upon the grass, and are swallowed by the ruminant. Soon afterwards the ova

contained in these segments are hatched in the intestines of the sheep, giving birth to microscopic larvae, which perform what may truly be termed a prodigious journey. From their native seat they force a route into the interior of the head, and, in the course of the journey, are obliged to penetrate through the most varied living tissues-the base of the skull even does not stop them. Instinctively they find one of the openings, and tear through the resisting tissue which fills it up. Having thus finally reached the brain of the sheep, they take up their abode in it, and there produce the Caenurus by which the host will infallibly be destroyed. This closes the cycle of existence

of the helminth, and the shepherd's dog incurs the grave suspicion of infecting the flock committed to his charge.

"Nevertheless, however great may be the complications attending a migration of this kind from one animal to another, and the subsequent journey through its tissues, if it is shown actually to take place, however mysterious the proceeding may appear, logically we are bound to admit its reality. But it is precisely at this point that we meet with, we will not say insurmountable, but with, at any rate, enormous difficulties. Let us see what these are.

"The Caenurus cerebralis, according to V. Siebold, Van Beneden, and other naturalists, would be the larva of Taenia serrata. But, on the other hand, this Taenia serrata, according to Küchenmeister, Van Beneden, Baillet, and V. Siebold himself, would appear to be the product of Cysticercus pisiformis, or of Cysticerus cellulosae, and C. tenuicollis, according to what V. Siebold further says.

"Here we find ourselves in the utmost embarrassment. It must be allowed, however, that zoologists have exhibited great ingenuity in this matter, if they have not been very exact. Immediately a Taenia is met with in any carnivorous animal whatever, the evil is at once imputed to his victim. The cat derives its worms from the rats and mice it devours; the wolf and the dog find theirs in the rabbits and sheep; man is indebted to the pig. But a scrupulous examination of the facts excites some doubts with respect to all this. It may be asked, for instance, how is it that the sheep, which does not eat the flesh of any animal, sometimes has its intestine filled with such a multitude of Taeniae as to have it completely obstructed by them? In an epizootic malady, which carried off many sheep in the neighbourhood of Rouen, in 1852, this was the case in almost every instance. If the tapeworms find themselves so well off in the intestine, why should the larva of some of them quit that locality, and be obliged to take a compulsory journey to the brain?

"The importance of this question, as regards agriculture, has not escaped M. Le Roy, Préfet of the Seine-Inférieure; and by him we have been instigated to experiment on a large scale on this grave subject.

"Several causes have evidently contributed to throw a degree of uncertainty on the results of experiments of this kind. In the first place, must be placed the natural frequency of the Entozoa which are employed upon the animals to which we profess to communicate them.