IV. 
THE FACTORS OF ORGANIC EVOLUTION FROM 
THE STANDPOINT OF EMBRYOLOGY. 
By Pror. EDWIN GRANT CONKLIN, 
Our knowledge of the mechanics of evolution must 
always depend in large part upon the ‘study of indi- 
vidual development. More than any 
other science, embryology holds the 
keys to the method of evolution. If on- 
togeny (life history of the individual) is 
not a true recapitulation it is at least a true type of evo- 
lution, and the study of the causes of development will 
go far to determine the factors of phylogeny or race 
development. 
The causes and methods of evolution are intimately 
bound up with those general phenomena of life, such as 
assimilation, growth, differentiation, metabolism, inher- 
itance, and variation; and the evolution problem can 
never be solved except through a study of these general 
phenomena of life itself. Our great need at present is 
not to know more of the course of evolution, but to dis- 
cover, if possible, the causes of growth, differentiation, 
repetition, and variation. All these general phenomena 
are most beautifully illustrated in the development of 
individual organisms, and because they are fundamental 
to any theory of evolution I shall dwell upon them 
100 
Embryology 
shows the meth- 
od of evolution. 
