8S THE GERM-PLASM 



allied species, such as Lycaena agestis : hence we must conclude 

 that these androconia have arisen by the transformation of 

 ordinary scales. This, however, presupposes the independent 

 variability of the scales which are to become changed phyleti- 

 cally, and consequently also their capability of being determined 

 from the germ onwards. Were this not the case, a single 

 scale could never have varied from the others hereditarily . In 

 Lycaena adonis there are 30,830 scales on the upper surface 

 of the wing.* If each of these is to be looked upon as cor- 

 responding to a determinate, the enormous number of about 

 240,000 determinants of the germ-plasm would result merely 

 from the scales covering the wings, provided that the upper and 

 under surface of the four wings possess each about the same 

 number of scales. 



I have endeavoured by direct experiment to ascertain the 

 lowest limit to the size of a determinate, — that is to say, the 

 size of the smallest determinates for a particular character of a 

 certain species. For this purpose I selected one of the Ostra- 

 coda, Cypris reptans, which multiplies parthenogenetically. and 

 in which it is easy to compare the different green spots on the 

 shell in the mother and daughter. It appears that the larger 

 spots are strictly transmitted, though this is not the case as 

 regards the very small ones, which consist of only one or two 

 pigment-cells. The form of these larger spots, which consist of 

 fifty or a hundred pigment-cells, also varies to some extent, so 

 that the number is here also somewhat inconstant. If partheno- 

 genetic reproduction could be looked upon as being purely 

 nniserial, it might be inferred that the determinates are not in 

 this case single cells, but groups of cells. Unfortunately, how- 

 ever, this experiment cannot be considered conclusive, for — as 

 will appear later on — the germ-plasm is here composed, just as 

 in the case of sexual reproduction, of dissimilar, and not of simi- 

 lar ids, and consequently variations in heredity may thus arise. 



We must conclude, even from the external coloration, that a 

 very considerable number of determinates exists in the case of 

 the higher Vertebrates. Thus most, if not all, of the contour- 

 feathers of a bird must be controlled by special determinants in 

 the germ-plasm, for they are independently variable hereditarily. 



* My assistant, Dr. V. Hacker, was good enough to make this calcula- 

 tion for me. 



