THE ULTIMATE SEX-ELEMENTS. 89 



it is possible to trace a direct cellular continuity, first of all, between 

 the ovum and early separated and reproductive rudiments; secondly, 

 between the latter and the future ova and sperms. There is not only 

 cellular continuity between the ovum which gives rise to parent, 

 and the ovum which gives rise to offspring, — that the cell-theory 

 demands, — but there is a continuity in which the character of the 

 original ovum is never lost by differentiation. In fact, there is a 

 continuous chain of reproductive cells quite apart from the body-cells. 

 It is in this sense that some of the authors quoted have spoken of the 

 continuity of the germ-ce//s. This is certainly true for some cases. If 

 it were true for all, the problems of reproduction and heredity would 

 be much simpler than they at present appear to be. 



Fig. 23. — The relation between reproductive cells and the body. — The continuous chain of dotted 

 cells at first represents a succession of Protozoa; further on, it represents the ova from which the 

 "bodies" (undotted) are produced. At each generation a spermatozoan fertilizing the liberated ovum 

 is also indicated. 



For in the present state of our knowledge we- can only speak of 

 the continuity of the reproductive cells, in exceptional or rather in a 

 small minority of cases. Alike in the higher vertebrates and the 

 lowly hydroids, the reproductive cells may appear late. After the 

 differentiation of the vertebrate embryo has progressed far, or the life 

 of the polyps continued for long, the germ-cells make their appearance; 

 and though we know of course that they are descendants of the 

 original ovum, yet we must allow, with Weismann, that in the form 

 of special cells they are now for the first time to be detected. There- 

 fore, Weismann says, ' ' a continuity of germ-cef/s is now for the most 

 part no longer demonstrable." 



Yet there is nothing that Weismann more strongly insists upon 

 than the reality of continuity between ovum and ovum. In what does 

 it consist, if a chain of ovum-like cells is only true of a minority of 

 organisms? It consists, according to Weismann, in the "keimplasma" 

 or germ-protoplasm. 



The germ-plasma is the distinctive part of the nucleus of the germ- 

 cell. It has an extremely complex, and at the same time persistent, 

 structure. It is the substance which enables the germ-cell to build 

 up an organism, the architectural living matter, and the immortal 

 bearer of all properties transmitted in inheritance. "In every devel- 

 opment, " according to Weismann, "a portion of this specific germ- 



