REVIEWS. 231 
than that between the laws which govern the transmission of character- 
istics among races perpetually clashing in the ‘struggle for existence," 
and those influencing the production of different breeds among animals 
enjoying the protection of the animal breeder. We, however, think that 
Professor Dawson would find it difficult to establish the truth of this 
rta 
existence necessarily lead to extinction. Darwin himself has shown that 
it leads to the extinction of those races which are not possessed of cer- 
tain advantages, and that it cannot according to physiological laws do 
otherwise than develop in a higher degree those points or changes in the 
favored races which enabled them to gain their first victories over their 
weaker brothers. 
The last objection, with regard to the lapse of time demanded for spe- 
cific changes ee to the Darwinian theory, is becoming stronger 
every day. eep sea dredgings have shown us that computations of 
geological time, side upon the thickness of rocks, and the presence of 
e 
other ia geological time, by imagining the lapse of ages and a corres- 
ponding modification of the organization of the animals included in the 
lowest bed. A simple change of fourteen degrees Fahrenheit may pos- 
sibly make the difference between a limestone compose ed entirely of 
organic remains, and a sandstone containing the fossil remnants of a 
totally distinct fauna, Hough both of these may have been composed of 
contemporaneous animals. 
he authors remarks upon Professor Cope's late paper before the 
American Association so well ua dp the substance of the new theory 
of derivation that we quote them 
"e ETNO Jast of these hypotheses wbich I shall notice, and, du oyn — the most promising of 
the * Origi G di th do tural Sciences, f and 
which is t based on the well known analogy between beaches changes, rank in the zoological 
scale and geological succession. It may be € by the remarkable and somewhat start- 
ling fact, that while no authenticated case exists of animals chan ging from one species to an- 
other, y are known to ch | from one zug or family t 
their individuality. Professor Dumeril, of Paris, and Professor Marsh h, of New Haven; have 
recenti y directed attention E. the fact that species of Siredon, reptiles of -= lakes of the 
f Mexico 
which, like our North American Menobranc. retain their 
set during life, when kept ih ape bien n a warmer ON MEI than mat w which is D 
0 them. s eir gills, and pass into a form hitherto regard: ofa 
pa amily, APOR us Amblyst toma. In voila case we mar either pete that the ! Ambistoms 
i it d be- 
nas 1L 
s maturity 
1 T, 1 of Spi- 
See Recent "nd of Deep Sea Fauna, by A. E. Verrill. Am 
ence and Art, 2d series, January, 1870. 
ladelphia, 1869, 
