74 



THE INVERTEBRATA 



o.wh. 



qam. 



^^^nu. 



Fig. 66. Stages in the life cycle oi Polystojnella. Semidiagrammatic. A, Me- 

 galospheric form, decalcified and stained. B, Shell of the same surrounded by- 

 escaping gametes. C, D, Conjugation. E, Zygote. F, Microspheric form, 

 decalcified and stained. G, Shell of the same surrounded by escaping amoe- 

 bulae. H, Young megalospheric individual with three chambers, gam. 

 gametes; i.wh. inner whorl of spiral; o.wh. outer whorl; nu. nucleus, 

 ret.pr. retral processes; i, first chamber. 



