XII.] CONJUGATION AND SEXUAL REPRODUCTION. 141 



la. 1^ -• 



4. 



5. 



6 



Fig. IV. 



Formation of spermatozoa in Pyrrhocons (modified from Henking). 

 I. Primitive sperm-cell containing nuclear spindle preparatory to divi- 

 sion : a. The equatorial plate as seen from the side, b. as seen from above. 

 2. Sperm-mother-cell. 3. Sperm-mother-cell preparatory' to the ' reducing 

 division.' 4. The same, after division of the chromatin-wreaths into 24 

 double idants. 5. First ' reducing division.' 6. Second 'reducing division.' 



