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selected and arranged ; but in a volume where so much 
of fundamental importance to the student is recorded, 
we could wish to see more discretion used in the 
transcription of certain hypotheses. We frequently find 
the most elementary facts set down side by side with the 
most daring generalisations. Nowhere is this more con- 
spicuous than on p. 85, where Hubrecht’s well-known 
Nemertean-Vertebrate hypothesis is referred to. The 
author mentions this with a caution it is true, but its intro- 
duction in the manner adopted, and with the illustrations 
given, is out of place. Again, a teacher is not justified in 
telling a novice as a frocés verbal in an elementary text- 
book that “ the Echinodermata, the Arthropoda, and the 
Mollusca form (p. 84) three very distinct branches or phyla, 
the common ancestor of which is to be sought for only in 
a simple worm.” Neither is he justified in asserting 
(p. 403) without further qualification than is here given, 
that “with the exception, then, that in Peripatus and 
Proneomenia, the anterior end of the nerve-cords is 
enlarged into a cerebral mass, we should appear to be 
able to see no essential difference between them and a 
Craspedote Medusa, save in fact that the Medusa has a 
complete nerve ring.” Statements such as the above may 
prove in the long run to be expressive of the truth, but if 
introduced into a text-book, efforts should be made to 
convey to the mind of the student some notion of what 
they involve. The beginner is too ready to rely upon his 
teacher and his text-book at all times, and the admixture 
of elementary facts with startling hypotheses is—in a work 
of this order—directly opposed to the true scientific prin- 
ciple. The natural tendency to generalise prematurely 
needs to be checked rather than otherwise, and if coun- 
tenanced by a teacher, it must lead to fallacies greater 
and more mischievous, than were those of the catastrophic 
school. 
There is a dangerous sketchiness about certain portions 
of this work. For example, on pp. 185 to 193 there is 
instituted a brief comparison of the great blood-vessels 
in the leading groups of animals. The descriptions given 
would lead one to infer that the ‘antennary, hepatic, and 
sternal arteries of the Crustacean, and the auricles of 
Mollusca, are serial homologues of the circular com- 
missures of a worm (here called “ transverse”) ; this is in 
fact stated (pp. 186, 189) to be the case. The argument 
used above applies equally well here, and we are at a loss 
to imagine the state of him who, with the aid of this book, 
shall try to ascertain the actual condition of these vessels 
in the admittedly all-important worm. 
When we reflect upon the advisability of placing this 
work in the hands of the average medical student, it 
must be admitted that it is not calculated to be of much 
service to him during his ordinary student life, except as 
a cram-book for the examination-room. The author has, 
by the terms of his agreement, pledged himself to produce 
a précis of all that is of first importance on the subject. 
The work will be very valuable as a remembrancer and 
book of reference to those who already know something 
definite of the broad principles of the science, and we 
conceive of it as calculated to be of especial service to 
geologists and others, whose work among the “dry bones” 
occasionally needs the light from within. So far as the 
medical student is concerned, it must be admitted that he 
is overtaught, and it is monstrous to reflect that there 
exist systems of medical education, such as have necessi- 
tated the production of this book as a “ Manual for 
Students of Medicine.” The days for “signing up” 
attendances on long courses of lectures upon zoology and 
botany are—or ought to be—numbered ; and if, as is 
most desirable, the biological leaven is to be introduced 
into the medical curriculum, it can only be done to good 
purpose along lines such as have been successfully laid 
down, mainly by Prof. Huxley. 
There is undoubtedly a need of a sound elementary 
book, which shall be up to date, on “the general structure 
of animals,” and Chap. III. of this volume supplies the 
want ina measure. The paucity of certain parts of this, 
however, is a serious obstacle to its adoption, for diagnoses 
such as are given for the Scaphopoda (p. 82), for the 
Copepoda (p. 68), and for the Siphonophora, are of little 
avail. 
Taking the book as a whole, the success with which 
the author has performed his task will be obvious to any 
one cognisant of the immensity of the field. Small errors 
cannot well be excluded from a work of this kind, but the 
volume contains some which ought to be rectified as soon 
as possible. For instance, there is no good ground for 
stating (p. 359) that the sesamoids are “no doubt to be 
explained by a reference to the primitively multiradiate 
condition of the vertebrate limb,” and there is something 
akin to a contradiction in the assertion (p. 140) that the 
teeth are “developed from cells of epiblastic origin,” and 
that there is ‘a community of origin between what have 
been well called dermal denticles and what we call teeth.” 
One remarkable instance of the manner in which errors 
of observation may be spread and distorted in the process 
of abstracting, is to be found on pp. 301 and 377, where 
we read that the telson “sometimes, though very rarely 
(Scyllarus), dears minute appendages.” We mention this 
as the author lays stress upon it, and unless we are mis- 
taken in the identity of the paper from which the above idea 
has been culled,! an attempt was merely made to show 
—and that unconclusively—that “the telson is a true 
body segment with lateral appendages, which are modified 
by cohesion and adhesion.” He who abstracts cannot be 
expected to verify the accuracy of every statement he 
reproduces—life is too short for that—but a matter such as 
the above should not have been allowed to pass. In defining 
the Arachnida (p. 72) it is stated that “the mouth is never 
placed so far back that any of the appendages become 
antennary organs.” This is but one view of a complicated 
and deeply involved question, and, even should it chance 
to be true in the end, it is but a deduction at the most, 
and its use here as a definition is unwarrantable. This 
same deduction underlies the statements made on p. 303 
under a similar head, and also the insertion of the foot- 
note uncalled for to p. 224. The first mention of the 
“transverse processes” of the vertebra (p. 314) as “given 
off” from the centrum is to be regretted, as it leads 
up to a complete misunderstanding of the nature of 
the component parts of the adult vertebra ; and, passing 
(pp. 324-25) from a somewhat jerky description of the 
vertebral column, it is doubtful how far it is wise to 
usher in so complex a subject as that of the skull, 
by a direct appeal to embryology. The statement 
(p. 325) that the trabeculz “never form more than an 
¥ Garrod, ¥ournal of Anatomy and Physiology, May 1871. 
