thinks sufficient for a learner before he approaches the study of his work. This is, in brief, the elements of Human Osteology, and some acquaintance with the digestive, the circulatory, the urinary, and the nervous systems of the human body, to be deduced from the study of specimens under the guidance of any of the current manuals. Having mastered this-the Oxford preliminary course-and thus acquired a certain power of observation, with a small amount of special knowledge, any "person entering for the first time upon the study of anatomy in the Oxford Museum" (Preface, p. 6) is considered competent by Professor Rolleston "to follow such a description as it gives in this work of the dissection of a mammal," the Common Rat. This we conceive a person of ordinary intelligence might do without such a previous course, especially with the preparation alluded to before him. But we are not informed how he is to obtain the additional knowledge he will require to understand the obscure technicalities and numerous statements concerning the anatomy of other animals, often rare ones, which he will find in the introduction to the Class Mammalia.

The author recommends that the study of the described preparations should precede that of the accounts in the introduction of the Class to which it belongs. We think this a wise proviso: for what beginner would not be deterred from advancing further who reads the first sentence of the introduction wherein the members of the Sub-Kingdom Vertebrata are characterised as "animals with bilaterally symmetrical bodies, divided internally into two perfectly distinct cavities, one of which is placed dorsally, and contains the principal nerve-centres, whilst the other contains the organs of vegetative life," although this is for our author simplicity itself. But why the author should advise that "the study of the description of the plates should be taken up only after the attainment of a considerable familiarity with actual specimens by the practice of Dissection," we do not see so clearly. These descriptions are unquestionably the easiest part of the book, and why the study of them should be postponed till the student has learnt for himself all the facts stated in them we fail to perceive.

The book itself consists of three parts: an introduction, a description of a series of preparations, and a description of twelve plates. The introduction occupies nearly 150 pages. It consists of a classification of the animal kingdom, and a condensed account of the anatomical differences on which the said classification is based. Distinct mention is, in general, made of the principal exceptions as to points of structure common to larger groups, found in any of their sub-divisions, or individual species. These exceptions are often great stumbling-blocks

to students, who are apt, in dissecting for themselves, without the assistance of a description of the actual animal studied, to mistake the exception for the rule; or, still worse, to misinterpret the structure of an exceptional form in order to bring it into conformity with the general rule, with which alone they are acquainted. In some few cases, on the other hand, the generality of Professor Rolleston's rules may be questioned; for instance, on page civ, he says of the Arthropoda, that antennæ, eyes, and auditory organs are all but invariably limited to their præoral cephalic segments. Very little is known of the auditory organs in this sub-kingdom, but among Insecta, in those in which they are best developed, the musical Orthoptera; they are situated either in the tibiæ of the fore-legs (Locustida Achetida), or along the insertion of the hind-legs (Acridia). Certain groups of pores at the base of the wings of some beetles and in the halteres of Diptera are also probably organs of hearing. In the Myriapoda and Arachnida, and in Myasis among the Crustacea, they are found in the endo-podite of the last post-abdominal segment, as Professor Rolleston himself mentions.

The arrangement of this part of the book is in some respects faulty, and renders it extremely obscure to those not previously acquainted with the classification adopted. Each sub-kingdom is first described as a whole: its primary divisions are next briefly stated; and a separate account of each Class is finally given in more or less detail. These accounts contain frequent mention of the peculiarities of the orders and minor sub-divisions of the Classes and even of individual species whose positions in their classes can only be known to the more advanced student, and whose bare names, accompanied by no reference to any work containing a description of them, can only confuse the ordinary reader. A table of the orders at least of each class, with the names of well-known examples, would in some degree remove this defect and might advantageously have been prefixed to the descriptions.

The sub-classes of Mammalia are given, and the orders Ratitæ and Carinatæ of Birds. Of the Reptilia only the existing orders are named, and the three orders of Amphibia are just mentioned, while the six orders into which the class Pisces are divided are separately described. None of the orders of the invertebrate classes are formally given. The description of the class Pisces occupies sixteen pages and is very complete; it is the best we have met with in any text-book, but far too many uncommon species are mentioned without any reference.

The description of other groups appears bare by comparison. That of Insecta, for instance, occupies only about five pages, and

some important points of structure are barely mentioned: thus, the organs of the mouth are dismissed in three lines, and nothing is said of their varieties of form on which all classifications of insects more or less depend. The wings have not even a sentence to themselves, but it is merely said that "each of the two posteriorly-placed segments [of the thorax] has also, ordinarily, a pair of unsegmented appendages, the wings, or the wing covers, articulated to it dorsally."

In treating of the Mollusca, Professor Rolleston differs from Professor Huxley in not admitting Pulmogasteropoda to the rank of a distinct class, not apparently attaching much weight to the character of curvature of the intestine which Professor Huxley possibly somewhat overvalues, although its constancy throughout large groups is apparently inexplicable if it be not due to a common parentage.

On the other hand the author always mentions, apparently attaching much importance to it, the presence or absence of an anus, and familiarises his readers with the little used terms "Proctuchous" and " Aproctous." This is a point manifestly dependent on external circumstances and therefore of little classificatory value.

Professor Rolleston adopts the sub-kingdoms first definitely proposed by J. V. Carus in 1853, and which Professor Huxley practically adopted in 1856, although his opinions have now somewhat changed. In this the author follows Gegenbauer, whose genealogical tree of these seven sub-kingdoms he copies in an amplified and somewhat altered form.

In this arrangement the three sub-kingdoms, Arthropoda, Vermes, and Echinodermata, correspond to the Annulata and Annuloida of Professor Huxley, which causes a considerable discrepancy between the two authors.

The description of the sub-kingdom Vermes and its classes is somewhat confused, the following remarks of reproduction, p. cxxv, being scarcely intelligible.

"Vermes may be either hermaphrodite or dioecious, either viviparous or oviparous; they may reproduce their kind either sexually or asexually, and their embryos may or may not go through a metamorphosis. When reproduction takes place asexually, it may take place either in the way of parthenogenesis, as in Rotifera and Ascaris nigrovenosa in its entoparasitic stage; or in that of metagenesis from a part of a protozooid, which is not differentiated as a sexual gland. Metagenesis is observable both in the highest and in the lowest of the vermes.

In some instances, at the time of the setting free of the deuterozooid produced by gemmation, both protozooid and deuterozooid may be in the asexual condition, as is ordinarily the

case with Nais and Chatogaster amongst Annulata, and with Microstomed amongst Turbellaria. In the case of certain other Turbellaria (Strongylostoma and Catenula), no other than this simple metagenetic form of reproduction has been, as yet, observed. When this form of reproduction alternates, as in the other Turbellaria, and in the Annulata just mentioned, with sexual reproduction, we have a series of phenomena before us which has been spoken of as "Digenesis with Heterogony." In some cases, as occasionally in Microstomeæ and in the Annelidan Syllidea and Protula, a sexual protozooid have been observed to give origin by gemmation to a sexual deuterozooid, furnishing thus an example of digenesis with contemporaneous heterogony. In some rare cases, the sexual organs of the protozooid have been observed to be of one, and those of deuterozooid of the other sex. In other cases the protozooid is always asexual, when it is known as a "nurse"; whilst the deuterozooids it gives origin to attain the sexual condition, either while still attached to the parent organism, as in the Taeniade amongst Platyelminths and Autolytus amongst Annulata; or subsequently to detachment from it as in Trematodes. These forms of reproduction may be spoken of as "digenesis with alteration of generations; inasmuch as the usual forms or stages of metamorphosis interposed between the products of sexual congress and another set of sexually perfect individuals may be regarded as sufficiently distinct and independent to merit the title of "generations."

To one who has not previously mastered the obscure subject of reproduction, with its, if possible, more obscure terminology, in which no two authors appear to agree, this passage can scarcely convey any meaning at all.

In separating the Gephyrea from the Annelida, or as he prefers to call the class the "Annulata proper," the author follows Gegenbaur. The absence in this class of distinct segmentation and of hermaphroditism; the structure of their vascular system which is distinctly analogous to, if not homologous with that of the Echinodermata, the complex convolutions of the digestive tract, and the frequent presence of respiratory trees, appear to afford good grounds for this separation. The subdivision of the Annuloida, under which head the author includes only the Scolecida of Professor Huxley, into the Nematelminthia, Rotifera, and Platyelminthia, is less satisfactory: that of Professor Huxley into six groups appears far better. But we are glad to find that while with Gegenbaur he classes the Chaetognatha of Professor Huxley with the Nematelminths, he does not so far follow his views as to introduce the Tunicates and Polyzoa among the Vermes.

The definition of the Platyelminths is careless. After stating

without qualification that they are devoid of an internal perivisceral cavity, on the opposite page he says that in the Nemertine which he includes in this class one exists. In other respects also this family fails to come under his general statements and renders the class utterly heterogeneous.

The Echinodermata are divided into four classes only, Holothuridea, Echinoidea, Asteridea, and Crinoidea; the Asterids. and Ophiurids being classed together. No mention is made of those extinct forms which are so completely intermediate in character that they cannot possibly be brought under any of these heads. Throughout the book those forms of life which have ceased to exist are scarcely even alluded to-a serious defect in some groups.

The author considers the jointed cirrhi on the stern or aboral surface of crinoids to be obscure indications that these animals are what Mr. Herbert Spencer would call tertiary aggregates. We cannot agree in this, they appear to us distinctly homologous with the similar cirrhi on the arms and not with the arms themselves; surely the author would not consider the arms to be tertiary and the individuals quaternary aggregates. Even that these cirrhi show the arms to be homologous with the tentacles of Holothuria, as the author asserts, we fail to perceive. The Ctenophora are wisely elevated to the rank of a distinct class of the Cœlenterata among the Protozoa; on the other hand we are glad to find the Radiolaria merged into the Rhizopoda.

In the description of this last sub-kingdom the author discusses the difficult question of the boundary between animals and vegetables. In this he denies the necessity of neutralising the ambiguous forms as Professor Häckel does under the title of Regnum Protisticum. In this we entirely agree with him, although not on his own grounds; but we fail to find much of value in the remainder of his remarks, which are devoted to raising imperfect criteria, only to upset them in the next sentence; while their sole conclusion is a hope that time may to some extent clear up the difficulty.

These remarks are feeble indeed as compared with the vigorous and philosophical disquisition of Gegenbaur on this subject which strikes at the very root of the matter, and, after showing that all attempts to draw the line by appeals to manifestations of volition on the part of supposed animals, must lead to different results with each observer, as they depend on subjective, not objective data, points out that no such distinct boundary ever exists in nature.

The second part consists of a description of fifty specimens prepared by the Demonstrator of Anatomy in the Oxford University Museum, and most of them exhibited by him in the