= mS trated by pe e a 1870. 
178 Recent Literature. [ March, 
or at least to the complete subordination of the other properties.” 
This extract from the introductory chapter strikes the keynote to 
the method of treatment of the subject. It is without doubt, and 
we have the word of a competent physiological expert for it, the 
most compact, clear and advanced text book of physiology in the 
language. The style is simple, clear and concise, and the preface 
is written in a happy vein with a dry humor that is unexpected 
but not the less telling and forcible. The book is designed chiefly | 
= medical students, ‘who have already mastered Huxley’s Ele- _ 
entary Lessons in Physio ology. We think the book would have _ 
eed improved by the addition of more illustrations than there are; 
not perhaps of machinery, but giving the results of important 
physiological experiments. The chapters on the Fundamental 
Properties of Nervous Tissues, and the Brain, are particularly 
good. ; | 
SEMPER’S EYES OF THE VERTEBRATE TYPE ON THE BACK OF 
SyaiLs.'—This work gives the results of Professor Semper’s ex- 
tensive and brilliant researches on the small organs of sight, or 
eye-specks, scattered over the back of a shelless snail (Onchidium) 3 
of which he has examined nineteen species, some of them living 
in the Philippine islands. In the author’s opinion these eye-specks 
have almost all the elements of the vertebrate eye. These eyes 
are different in structure from the tentacular eyes of the Onchidium 
and other land snails, as the nerve arising from them are not 
thrown off from the cerebral ganglion, but from the visceral nerve- 
centre. Prof. Semper describes the arrangement, size and num- 
ber of the dorsal eyes, with their structure, and gives remarks on 
their developmental history; a comparison of the dorsal eyes of 
chidium with those of other animals, discusses the biological 
Soteiderations resulting from these facts, and in the closing re- 
marks of a theoretical nature, discourses on the primitive origin 
of dorsal eyes, and on the “ Monophyletic or poi phieno ae 
vance in the formation of the simplest dorsal eyes.” 
bear witness to the beauty of the microscopic sections, ee 
glanced at some of them through the kindness — Professot 
Semper during his visit in the United States last a The 
plates are colored lithographs, and are effectively aid "skillfully 
drawn. 
ZIRKEL’S MICROSCOPICAL PETROGRAPHY.*— This espis has — 
in the hands of Zirkel, Boricky and others in Germany and Aus- 
tria, attained a good degree of develophiont but little attention 
1 Reisen im Archipel der Philippinen, von Dr. C. SEMPER. Zweiter Theil. Wis- 
eaaa eean Resultate. Drittu Band. Land- Moliusken. Ueber “ec organe vom — 
pus der Wirbel thier augen auf dem Rücken von Schn . n Dr. C. Sem- 
; = Mit fiinf Tafeln Colorirter abbildungen, Wiesbaden, sas. phy pp- 46. 
2 United py Geological Exploration of the Fortieth Parallel. Clarence Kap : 
Geologist-in-Charge. Microscopical na pie my FERDINAND ZIRKEL. 
