PANDORINA 



193 



Fig, 25. — Pandorina. A, colony (ccenobium) of 16 cells in the 

 vegetative state. B. reproductive condition — each -.ceU of the 

 coenobium has divided to form a new daughter ccenobium. C, 

 free-swimming gametes of various sizes ; a, b, conjugation of 

 gametes of equal size ; c, of unequal size i d, zygote still retaining 

 the flagella of the gametes which formed it ; e, conjugation 

 between small (male) gametes which have originated elsewhere 

 and large sluggish (female) gametes which have remained where 

 they were formed by division ; /, walled zygote ; g, escape of 

 contents of zygote as a free-swimming zoospore which will form 

 a new coenobium by division. 



13 



