1895.] Search for the Unknown Factors of Evolution. 431 
ism. Experiments upon color, therefore, afford a marked illus- 
tration of the necessity of drawing a sharp distinction between 
cenogenic and palingenic variations. We have, in many cases, 
been mistaking repetitions of ancient types of structure for 
newly acquired structures. When the pale Proteus is taken 
from the Austrian caves, placed in the sunlight, and in the 
course of a month becomes darkly pigmented, there are two 
interpretation of this pigmentation; either that we have 
revived a latent character, or that we have created a new 
character. The latter interpretation can alone be taken as a 
proof of Buffon’s factor when it is found to be followed by 
hereditary transmission. 
Poulton,” as a supporter of Neo-Darwinism, takes this view, 
in reply to Beddard and Bateson, and as an induction from his 
beautiful and exact experiments upon the coloring of lepi- 
dopterous larve. After producing the most widely various 
colorings and markings by surrounding the larve during on- 
togeny with objects of different colors, he urges that the 
changes thus directly produced simply revert to adaptations to 
former conditions of life, in other words, that they are palin- 
genic. Whether this interpretation is correct or not, Poulton 
proves that, no matter how stable certain hereditary characters 
may appear to be, repetition in ontogeny depends upon repe- 
tition in environment, and that there are wide degrees of 
ontogenic variations which do not become phylogenic at least 
in several successive generations. 
From many other analogous researches we gather the follow- 
ing principle to which far too little attention has been paid in 
the study of the phenomena of variation in their bearing upon 
the factors of evolution: It is that ontogenic repetition depends 
largely upon repetition in environment and life habit, while 
ontogenic variation is connected with variation in environment and 
life habit. If the environment be changed to an ancient one, 
then ontogenic variations tend to regression or reversion (i. e., 
palingeny) or practically to repetition of an ancient type. It 
16 E. B. Poulton: Further experiments upon the color-relation between aay 
mace larve, pup, cocoons, and imagines and their surroundings. 
EB t. IV, p. 293. London, 1892. (Contains a reply to Beddard cad 
Bateson) 
