1 62 THE EVOLUTION OF SEX. 



This supposition appears to us to be open to criticism, (i.) That the 

 nuclei are alone important in fertilisation, and that the cell substance is a 

 mere adjunct, cannot be said to be proved, and we have already noted some 

 of the facts which tell the other way. (2.) The structure of a cell is 

 recognised by all to be an expression of its dominant protoplasmic pro- 

 cesses. The sex-cells are usually highly dimorphic, and even Strasburger 

 allows that there may be minor differences in their nuclei, as well as the 

 marked divergence in their cell-substance. The nucleus cannot be 

 regarded as an isolated element, but as one which shares in the general 

 life of the cell. We have already interpreted the differentiated male and 

 female cells as respectively katabolic and anabolic, and see no reason for 

 doubting, in spite of structural resemblance in the rough features of nuclei 

 (all that we know), that this difference saturates through the elements. (3.) 

 If the only important matter be the quantitative restoration of the original 

 amount of germ-plasma in the female nucleus, it seems difficult to under- 

 stand the phenomena of conjugation, whether permanent or transitory, from 

 which we believe fertilisation to have originated. (4. ) That the normal ovum 

 should lose half its quantity of germ-plasma, only to regain a similar quantity 

 in fertilisation, certainly appears a curiously circuitous process. (5.) The 

 occasional possibility of inducing division by replacing the sperms with 

 other stimuli, seems to point to a dynamical or chemical action, which 

 Weismann denies. 



We are bound, of course, to admit the importance of the established 

 facts of nuclear union, and agree with Boveri, that the complexity of the 

 morphological facts shows the present impossibility of supposing that they 

 can be fully expressed in chemical terms. But a due impression of the 

 marvellous "individuality " of the nuclear elements may be combined with 

 a general physiological interpretation of the entire process. 



It has been already noted, in regard to the origin of fertihsa- 

 tion, that the ahnost mechanical flowing together of exhausted 

 cells is connected by the stages of multiple conjugation with 

 the ordinary form of the latter, while the respective differentia- 

 tion of the two elements effects the transition to fertilisation 

 proper. Historically, then, fertilisation is comparable to mutual 

 digestion, and, though bound up with reproduction, has arisen 

 from a nutritive want. With the differentiation of the elements 

 on anabolic and katabolic lines, the nature of the fertilising act 

 becomes more definite. The essentially katabolic male cell, 

 getting rid of all accessory nutritive material contained in the 

 sperm-cap and the like, brings to the ovum a supply of 

 characteristic waste products or katastates, which stimulate the 

 latter to division. The profound chemical differences, surmised 

 by some, are intelligible as the outcome of the predominant 

 anabolism and katabolism in the two elements. I'hc union of 

 the two sets of products restores the normal balance and 

 rhythm of cellular life. Rolph's suggestion is thus included 

 and defined. 



