NOTICES OF NEW BOOKS. 439 
logical, sometimes it is mammalogical, and not unusually ento- 
mological; hence this publication, from Dr. Gadow’s own stand- 
point and study, supplies valuable material for the evolutionist 
as well as information for the zoologist. We do not allude to 
the botanical and archeological chapters—chacun a son gotit ; we 
are now addressing zoologists in ‘The Zoologist.’ 
The Origin of Vertebrates. By Watter Hotproox GasKkELL, 
M.A., LL.D., &&. Longmans, Green & Co. 
In the author’s introduction to this important book he writes : 
“‘T have been told that it is impossible for one man to consider 
so vast a subject with that thoroughness which is necessary, 
before any theory can be accepted as the true solution of the 
problem.” The truth of this statement becomes patent to any 
conscientious reviewer of Dr. Gaskell’s volume, for if ‘‘ zoology 
without physiology is dead, and physiology in many of its de- 
partments without comparative anatomy can advance but little,” 
an ordinary naturalist who may study ‘The Origin of Verte- 
brates’ must be well equipped to weigh the evidence with that 
judicial capacity which only special knowledge can supply, and 
without which no impartial verdict can be given. The theory 
advanced is best given in the author’s own words, and is “ that 
the so-called central nervous system of the vertebrate-is in 
reality composed of two separate parts, of which the one, the — 
segmental part, corresponds to the central nervous system of the 
highest invertebrates, while the other, the unsegmented tube, 
was originally the alimentary canal of that same invertebrate.” 
The theory is very largely a physiological one, but an excellent 
summary at the end of each chapter enables the student to both 
understand the author’s progress with his argument and to again 
study his facts advanced in support of the different conclusions 
claimed in that summary. ‘This method is exceedingly fair and 
thorough; we must bring both thought and knowledge to esti- 
mate the strength of this proposition, but we are never bewil- 
dered; the facts in its support are clearly marshalled and ably 
stated, and if some readers may not follow Dr. Gaskell in the 
whole strength of his conclusions, none can fail to find his time 
and thought have been rewarded by an exceptional exploration in 
