THE GERM-PLASM THEORY 75 



more closely. The germ-plasm of a given cell is, 

 he teaches, made up of a number of " ids," each 

 of which is the complex of primary constituents 

 necessary to the production of a complete in- 

 dividual. A compound of several of these is an 

 " idant." The " id " is made up of " determin- 

 ants," and there is one determinant for each 

 portion of the body which is capable of independ- 

 ent variation. Some of these must belong to very 

 minute areas. 



" Thus, for instance, in many human families 

 there occurs a small pit, hardly as large as the head 

 of a pin, in the skin of the ear, whose transmission 

 I have observed from the grandmother to the son 

 and to several grandchildren. In such a case there 

 must be a minute something in the germ-plasm, 

 not present in that of other human beings, which 

 causes the origin, in the course of development or 

 this little abnormality in the skin." Vol. i. 355. 



The " minute something " is the determinant 

 for the part. It is obvious from this that there 

 must be an enormous number of these determin- 

 ants in the simplest form of body. But under 

 further developments of Weismann's system the 

 multiplicity becomes something almost unthink- 

 able. For it is clear that if we are to have a separate 

 determinant for every part of the body capable of 

 independent variation, and if as we know is the 

 case the caterpillar and the butterfly, which 

 comes from it, are both of them capable of in- 

 dependent variation, then the caterpillar must 

 carry in its body the determinants which are 



