THE PHYSICAL BASIS OF HEREDITY. 



I6 5 



sizes (Fig. 7, D}. These coalesce, round up into a spher- 

 ical cell (Fig. 7, E, F), which soon develops an envelop- 

 ing cellulose wall, and passes as a " zygote " into a rest- 

 ing stage (Fig. 7, G}. In this condition the organism 



FlG. 7. Development of Pandorina morum : A, a swarming family ; 

 B, a similar family divided into sixteen daughter families ; C, a sex- 

 ual family, the individual cells of which are escaping from the com- 

 mon gelatinous investment; D, E, conjugation of pairs of swarm 

 spores ; F, a young zygote ; G,a mature zygote ; H, transformation 

 of the contents of a zygote into a large swarm cell ; I, the same, 

 free ; J, a young family developed from the latter ; K, a free swim- 

 ming swarm spore. (After Pringsheim.) 



