THE PHYSICAL BASIS OF HEREDITY. 165 
sizes (Fig. 7,.D). These coalesce, round up into a spher- 
ical cell (Fig. 7, £, 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 
Fic. 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.) 
