i88 



ORIGIN OF SEX AND OF THE SOMA 



times the process of division continues further, so 

 that by repeated bipartitions from eight to sixty-four 

 cells are formed, their size varying inversely as the 

 number produced. In some species they secrete cell 

 walls, in some their bodies are naked, but in other 



Fig. 21. — Conjugation of Chlamydomonas : a, gametes approaching 

 one another ; b and c, stages of fusion ; d, zygote. (After Dill.) 



respects they are identical with the ordinary indi- 

 viduals. When these larger numbers of small daughter 

 cells are produced, they do not, as a rule, at once 

 grow into full-sized individuals, but conjugate in pairs, 

 and are hence called gametes.^ In the process of con- 

 • Greek yanico, marry. 



