130 THE EVOLUTION OF SEX. 



from their neighbours ; and if their area of exploitation be 

 sufficiently large, emphatically anabolic cells or ova result ; 



I oh'ox glohator, a colonial Alga or Infusorian, showing the 

 ordinary cells (c) that make up the colony (or body), and 

 the special reproductive cells (a, d), both male and 

 female. — After Cohn. 



while if their area is reduced by the presence of numerous 

 competitors struggling to become ova, the result is the forma- 

 tion of smaller, less anabolic cells, which become ultimately 

 viale, segment into antherozoids, meantime losing their vegeta- 

 tive greenness and becoming yellow. In some species, distinct 

 colonies may, in the same way, become predominantly anabolic 

 or katabolic, and be distinguishable as completely female or 

 male colonies. Thus, again, we reach the conclusion, of a 

 predominant anabolism effecting the differentiation of female 

 elements, and of katabolism as characteristic of the male. 



^5 6. Corroborative IlIiisfraiio?is. — If the anabolic and kata- 

 bolic contrast, so plainly seen in the sex-elements, be the funda- 

 mental one, we must expect to find it saturating through the 

 entire organism. We have already drawn attention to the 

 occurrence of yolk glands in association with ovaries. Or 

 again, in the cells of a developing anther an enormous number 



