MoJiJ'icatioii of Germinal Constitution of Organisms iij 



ous conditions, especially high temperature accompanied 

 by low relative humidity. Such variants have been found 

 in nature, some of them are known to breed true, and 

 others are produced in experiment. 



Fig. 74 shows a photograph of a demonstration case 

 exhibiting the results from an experiment of this kind. 

 Here the parent pair are shown producing the two first lots 

 of eggs which developed into normal individuals which 

 were in following generations true to type, while the third, 

 fourth, and fifth lots of eggs were experimented upon and 

 gave in each modified t>ioes, pallida and miiuita, as well as 

 some normals. These dift'erent types, when inbred, came 

 true to tjrpe in subsequent generations, as shown. 



Another divergent type which arose in the same series 

 of experiments is one in which the pigmentation is increased, 

 that is, the amount of dark pigment in the color [jattern 

 gaA^e the resulting individual a different appearance from that 

 of the parent species. Both pallida and melanicum (Fig. 

 73. 1) were true breeding germinal variations, and pallida 

 when given a fair start showed itself, at least in certain 

 cultures, to be capable of sustaining itself in competition with 

 the parent species; mclanicnni., however, did not exhibit any 

 such potentiality. 



If a form like L. pallida were to develop in an arid area 

 it would be recognized, as I have suggested, as a step in the 

 process of evolution, and it would be directly attributed, if 

 it were found in nature, to the conditions under which it 

 was living, and its existence would be explained either by 

 natural selection, or some other of the current hypotheses. 



Other modifications which have arisen from L. drccin- 

 lincata, especiall}- in the modification ol the h>7)odermal 

 lipoid pigments, are distinctly not the increase or decrease 



