1895.] Psychology. 687 
ated, violent stage of the same phenomena. When the vortex currents 
become violent, watery liquid accumulates between the cleavage cells 
so that they are separated and henceforth develop separately to forma 
twin. 
It is to be regretted that the excellent observations recorded do not 
bear more forcibly upon the hypothesis advanced. 
PSYCHOLOGY.’ 
Mental Development inthe Child andthe Race: Methods 
and Processes. By,JAmMEs Mark BALDWIN, M.A., Pa.D., STUART 
PROFESSOR OF PsyYCHOLOGY IN PRINCETON UNIveERsitTy.’—Prof. 
Baldwin’s latest book will prove of no less interest to the biologist 
than to the psychologist. There is a growing feeling that biology, 
the science of life at large, and psychology, the science of the inner 
life, since they deal with facts of the same order, must ultimately 
express these facts in essentially the same conceptions. To biology 
we must look for the most generalized expression of those conceptions; 
it will be the duty of the psychologist to apply them in his narrower 
field and to restate them with such additions and limitations as the 
facts demand. Yet, just because his field is the narrower, we may 
expect of him suggestions which will aid the biologist in his work. 
This is what Prof. Baldwin has undertaken to do. While studying 
imitation in the infant, he tells us, he was struck by the important 
part played by it in the development of the individual. This led him 
to read again “the literature of biological evolution with view to 
a possible synthesis of the current biological theory of organic adap- 
tation with the doctrine of the infant’s development,” and this book 
is the outcome. It is full of original and suggestive material and 
I think I can do no better than give the readers of the NATURALIST 
a fairly complete outline of its contents. 
The arrangement of the book is open to criticism. The first six 
chapters deal with certain special problems and are intended to 
develop inductively the fundamental conceptions of dynamogenesis 
1 This department is edited by Dr. Wm. Romaine Newbold, University of Penn- 
sylvania. 
2 Macmillan & Co., 1895. Price, 2.60. 
