1886. ] Recent Literature. 143 
At the tip of the tail they stand in the position of the caudal neu- 
ropodia and notopodia of errant annelids, but are not, as in them, 
constituted of palea, bristles, etc. In the anterior dorsal region 
of Scyllium, these bodies are in the position of neuropodia. 
It will thus be seen that Mayer supplies a most important set 
of data which lend support to the views of Dohrn as to the mean- 
ing and origin of the median and paired fins, since that author has 
contended that the relations of these peripheral structures to the 
axis of the body are to be determined by the relations they bear 
to the myotomes which send out muscular buds into the fins, and 
not on the basis of the relations to the cartilaginous appendicular 
skeleton or spines, as held by most other morphologists. 
The table which Dr. Mayer gives to illustrate the varying rela- 
tions of the same metameric elements of the median fins to the 
point where the vertebral axis becomes diplospondylic are also of 
great interest, not only morphologically, but also taxonomically. 
or the first time in the history of the subject, in fact, we have 
presented in this paper a tabulated statement of what are the 
actual relations. of the metameric elements of the vertical fins to 
logical methods. It is to be regretted that the author does not 
give a brief summary of his results at the close of the paper 
These researches, it may be remarked in conclusion, also show 
that in Scyllium there is developed a posterior terminal, vermi- 
form section of the embryo which corresponds to what the writer 
has called an opisthure. Though it is obvious that this opisthure 
is rudimentary and evanescent, as it soon becomes inconspicu- 
ous. Some of the Elasmobranchii, therefore, pass through what 
the writer has termed an archicercal stage. 
The results reached by Dr. Mayer also afford important evi- 
dence in support of the archistome theory, published by the 
writer in this journal recently..—/John A. Ryder. — 
_ Bower anv Vines’ Pracricat Botany.?—One of the significant 
signs of the times, so far as botany is concerned, is the multipli- 
cation of books which are designed to encourage the practical 
Study of plants in the microscopical and physiological labora- 
tories, A few years ago, such a thing as a laboratory manual for 
the guidance of the botanical student was unheard of; now we 
* AMERICAN NATURALIST, November, 1885, pp. 1115-1121. 
* A Course of Practical Instruction in Botany. By F. O. Bower, M.A., F.LSe 
Lecturer on Botany at the Normal School of Science, South Kensington; and SID- 
NEY H. Vines, M.A., D.Sc., F.L.S., Fellow and Lecturer of Christ’s College, Cam- 
bridge, and Reader in Botany in the University, With a preface by W. T. THis- 
; .A., C.M.G., F.R.S., F.L.S., Assistant Director of the Royal 
ere Kew. Part 1., Phanerogamæ-Pteridophyta. London, Macmillan & Co., 
