250 The American Naturalist. [March, 
of bone, using the word plasticity not in a physical sense merely, but to 
include absorption under pressure, will probably account for much 
structure in the foot and elsewhere, especially the connection with the 
joints, and in the fields of variation and correlation.” In the second 
proposition he says that facts have been adduced by him which are 
inconsistent with the theory that the size of bones has been increased 
by the stimulus they receive, and with the theory that regions of 
growth are determined by regions of pressure and strain. “ The testi- 
mony of the literature as to the latter point he says is conflicting.” I 
have shown that the supposed conflict is due to a misunderstanding on 
the part of the author of this paper. The proposition that pressure 
does not affect growth is in contradiction to the admission made by the 
author in his first proposition, where he admits that pressure determines 
structure; for in such change of structure there is always growth. 
inally Mr. Cary remarks “ That race changes follow those produced 
in the individual life, or that they are directly caused by their mechan- 
ical surroundings, I do not think it has been satisfactorily shown. ” 
The fact that the characters of bone structure admitted by-Mr. Cary to 
have had a mechanical origin appear in the young before birth, is 
evidence that race characters are produced, and that they are produced 
by mechanical surroundings. 
Such criticisms as are contemplated by the author of the paper 
reviewed above, are important and are what the subject needs. It is 
along the line followed by him that the ultimate demonstration of the 
problems involved will be made. We trust that we shall hear from 
him again in this field, and that in his labors he will be well supplied 
with the phylogenetic details as a foundation. 
E. D. COPE. 
Earle on the Species of Coryphodontide.’—In preparing 
this paper Mr. Earle had the advantage of the use of the material in 
the collections of the New York American Museum of Natural His- 
tory, and the private collection of Professor E. D. Cope. He presents 
us with a brief résumé of the results of his comparisons, and adds con- 
siderably to our knowledge of the characters of the skeleton and 
dentition of some of the species. He gives a list of the described 
species, which number twenty-one, and which were referred by Cope 
to five genera. He concludes that these should be reduced to ten 
“Revision of the species of Coryphodon, Art. xii, Bull.Am. Mus. Nat- 
History New York, iv, pp. 149-66; Oct. 18, 1892. 
