Modification of Germinal Constitution of Organisms 215 



attained full sexual maturity and complete development 

 of all qualities and attributes. 



A check upon the possible latent characters is more 

 difficult, but in this material it is easily carried out in one 

 of two ways: First, only pedigreed material was used in 

 experiment. This material has always been tested by cross- 

 ing within and without the species to discover, as far as 

 possible, any characters which might be present in invisible 

 conditions. Thus far, no attributes of this description have 

 been discovered. Second, a check w^as kept upon this 

 possible source of error in the following way: these beetles 

 have the habit of maturing their eggs in definite rotation; 

 that is, a batch of eggs is developed, fertilized, and laid; 

 then a time interval elapses during which another batch of 

 eggs is being developed, and this is repeated many times, 

 thus giving isolated lots of eggs, each separated from the 

 one before by a time interval of from two to sixty days, 

 or even more, and any one of which may be subjected to 

 experiment and the others used as controls. In many of 

 these experiments color has served as a useful character for 

 study and the results from the experimental modification 

 of color may be presented first. 



Experimental modification of color. — Color modifications 

 are of two distinct kinds: changes in the pigment itself, 

 and in the localization thereof. The first is a chemical 

 change produced by a rearrangement of the chemical 

 activities existing between a chromogen and an enzyme 

 which brings the color-forming compounds into existence, 

 while the latter is a change in the localization. 



Variations in color usually are either accentuations or 

 diminutions of existing color, and these changes are perma- 



