CONFOEMITY TO TYPE 233 



become pervaded by it as a connected network. Proto- 

 plasm, including both trophoplasm and idioplasm, he 

 considered to be compounded of exceedingly minute 

 units no larger than a molecule of albumen, to which he 

 gave the name micella. These were capable of multi- 

 plication, not by division, but through the formation of 

 new ones between those already existing. The ger- 

 minal cells contain both trophoplasm and idioplasm, the 

 latter governing the growth of the former as it increases 

 itself. In this theory the thought of the continuity of 

 the germinal substance is foreshadowed. Sedgwick 

 Minot suggested that Nageli's "idioplasm" might be 

 identified with the nuclear chromatin. 



Gustav Jager in 1878 seems to have been the first to 

 express the idea that in the higher organisms the body 

 consists of two kinds of cells which he called the " auto- 

 genetic" and " phylogenetic, " respectively, and that the 

 latter or reproductive cells are not the product of the 

 former, or body cells, but are derived directly from the 

 germ cell of the parent. 



Rauber in 1880 conceived that the effect of fertilization 

 was to convert a portion of the egg, namely, the personal 

 part, into the form of a person; the other portion does 

 not experience this effect, for it has stronger powers of 

 persistence. 



Nussbaum in 1880 also foreshadowed the idea of the 

 continuity of the germ cells, and supposed that the seg- 

 mented ovum divides into the cell material of the indi- 

 vidual and the cells for the preservation of the species. 

 These ideas remained unnoticed until Weismann's 

 theory was evolved in 1892. 



The theory of the "germ plasm" was the work of 

 Weismann and, though it may be subject to valid 

 objections, contains so large a proportion of truth that 

 it has taken a strong hold upon the thought of the day 

 and forms the basis of a large part of biological specula- 

 tion. It is essentially a cytological theory, and though 

 it follows the thought expressed in the theories preceding 



