THE INFLUENX'ES OF ENVIRONMENT 275 



the old species of the Ice age, were accustomed to greater cold, but 

 this idea is contradicted by the experiments of E. Fischer, which go 

 to show that the same aberrations are evoked by abnormally high 

 temperature. That the old ancestral determinants are present in 

 dijferent numbers in the germ-plasm of the modern species, I am 

 inclined to infer from the fact that among a large number of 

 experiments made by me in the course of several years the aberra- 

 tions have always occurred in verj- different numbers in the different 

 broods, although the greatest care was taken to have the conditions 

 as nearly alike as possible ; absolutely alike, of course, they never 

 can be. 



But it would lead me too far if I were to enter on a detailed 

 discussion of these cases, which have not yet been fully worked up : 

 only one thing more need be mentioned, that is, that the aberrations 

 induced by cold are to a certain extent transmissible. Standfuss 

 first succeeded in making some aberrant specimens of Va/aes^a urticos 

 reproduce, and from their eggs he procured buttei-flies which showed 

 a much slighter deviation from the normal, which however was still 

 so decided that it could not be regarded as due to chance. I myself 

 succeeded in doing the same, but the deviation in this case was 

 much slighter. But that these observed cases are rightly referred 

 to the cold to which their parents had been subjected is proved by 

 other observations recently published b}" E. Fischer. These refer 

 to one of the Bombycidse {Arctia foy'tt), which flies by day, and accord- 

 ingly has a gay and very definite marking and coloration. A large 

 number of pupae were exposed to cold at 8 C, and some of these 

 resulted in striking and very dark aberrant forms (Fig. 129, A). 

 A pair of these yielded fertilized eggs; in the progem*, which were 

 reared at a normal temperature, there were among the much more 

 numerous normal forms a few (17) which exhibited the aberration 

 of the parents, though to a considerably less degree (Fig. 129, B). 



This shows that the cold had affected not only the wing-primordia 

 of the parental pupa?, but the germ-plasm as^ well, and at the same 

 time that this latter variation was less marked than that of the 

 determinants of the wing-rudiments. This gives rise to an appear- 

 ance of the transmission of acquired characters. 



In the case of many of these cold-aberrations in Lepidoptera the 

 cold gives rise to variations, but does so not by creating anything 

 new, but by giving the predominance to primary constituents which 

 have long l)een present, but are usually suppressed, and so it is also 

 among the plants. I have in mind, for instance, the interesting- 

 experiments of Vochting on the influence of light in the production 



T 2 



