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. 1 In the process of con- 



Greek yct/i&o, marry. 



