OTHER PROTOZOA 



95 



are soon cast off and the zygote sinks to the bottom of the pond 

 where it secretes a thick red wall about itself (VI- VII). It re- 

 mains in this condition throughout the summer, becoming dry 

 when the pool of water in which it lives evaporates. In the 

 autumn activity is again resumed. The zygote produces from 



FIG. 45. Pandorina morum. I, vegetative colony ; II, formation of daughter 

 colonies; III, escape of gametes; IV, V, VI, VII, fusion of two 

 gametes to form a zygote ; VIII, IX, production of swarm spores by a 

 zygote ; X, vegetative colony formed by a swarm spore. (From Olt- 

 manns.) 



