62 THE FIRST PRINCIPLES OF HEREDITY 



Fig. 37) as an outgrowth of the germ-cells, which, with 

 the progressive evolution of species, has become ever 

 larger and more complex. 



The germ-plasm, with its Determinants, Ids and Idants, 

 has, according to Weismann, a definite architectural 

 arrangement, which in some way is representative of the 

 body, but is by no means identical with it. (This latter 

 notion would involve a revival of the old crude idea of 

 preformation, which considered the germ to contain a 

 complete individual in miniature.) The order of the 

 ontogenetic stages* of the embryogenesis is due to the 



FIG. 37. THE RELATION BETWEEN THE REPRODUCTIVE CELLS AND 

 THE BODY. 



(From Geddes and Thomson, " The Evolution of Sex.") 



The continuous chain of dotted cells at first represents a succession 

 of protozoa ; further on it represents ova, from which the 

 " bodies " are produced. At each generation a spermatozoon 

 fertilizing the liberated ovum is also indicated. 



inherent forces in this structural arrangement of the germ- 

 plasm. As the body passes through its different phases 

 of development by the fission of the primitive cells, the 

 right determinants multiply and come into activity, sever 

 themselves from their group-connections, and determine 

 the character of each cell as it appears. The remainder of 

 the determinants for all the later cell-sequences are 

 carried forward in a latent state, until one determinant 

 after the other falls out of the complex group of deter- 

 minants to determine its own cell, so that finally only one 



* Ontogenetic stage = each single stage of the embryonic develop- 

 ment. 



