POLYMORPHISM. 



101 



in a labile or sensitive condition and therefore capable of being de- 

 flected by differences in the trophic stimuli acting on the larva. Ac- 

 cording to Emery : " The peculiarities in which the workers differ from 

 the corresponding sexual 

 forms are, therefore, not in- 

 nate or blastogenic, but ac- 

 quired, that is somatogenic. 

 Nor are they transmitted as 

 such, but in the form of a 

 peculiarity of the germ-plasm 

 that enables this substance to 

 take different developmental 

 paths during the ontogeny. 

 Such a peculiarity of the germ 

 may be compared with the 

 hereditary predisposition to 

 certain diseases, which like 

 hereditary myopia, develop only 

 under certain conditions. The 

 eye of the congenitally myopic 

 individual is blastogenetically 

 predisposed to short-sighted- 

 ness, but only becomes short- 

 sighted when the accommoda- 

 tion apparatus of the eye has 

 been overtaxed by continual 

 exertion. Myopia arises, like 

 the peculiarities of the worker 

 ants, as a somatic affection on 

 a blastogenic foundation. 



" With this assumption the problem of the development of workers 

 seems to me to become more intelligible and to be brought a step 

 nearer its solution. The peculiarities of the Hymenopteran workers are 

 laid down in every female egg; those of the termite workers in every 

 egg of either sex, but they can only manifest themselves in the presence 

 of specific vital conditions. In the phylogeny of the various species of 

 ants the worker peculiarities are not transmitted but merely the faculty 

 of all fertilized eggs to be reared as a single or several kinds of 

 workers. The peculiar instinct of rearing workers is also transmitted, 

 since it must be exercised by the fertile females in establishing their 

 colonies." 



The views above cited show verv clearlv that authors have 



FIG. 62. Heads of workers of Dorylns 

 affinis drawn to same scale to show differ- 

 ences in size .and in number of antennal 

 johits. (Emery.) a. Soldier, or worker max- 

 ima, ii mm. long; b, worker major 5 mm. 

 long; c, worker minima with ii-jointed an- 

 tennae ; d, worker minima with to-jointed an- 

 tennae : e. with g-jointed antennae, /, with 8- 

 jointed antennae : /', antenna of same enlarged. 



