252 GERM-CELL CYCLE IN ANIMALS 



this is the pachytene stage. The filaments then 

 begin to unravel (Fig. 62, 6-7), become distributed 



FIG. 62. Prophases of the heterotype division in the male Axolotl. 

 1 , nucleus of sperm ogonium, or young sperm ocyte ; 2, early lepto- 

 tene ; 3, transition to synaptene ; 4, synaptene with the double 

 filaments converging towards the centrosome ; 6, contraction fig- 

 ure; 6, 7, pachytene; 8, early; 9, later diplotene ; 10, the hetero- 

 typic double chromosomes; the nuclear membrane is disappearing. 

 (From Jenkinson, 1918.) 



throughout the nucleus, and finally split into two 

 threads (Fig. 62, 8-9) ; this is the diplotene stage. 

 The pairs of filaments finally shorten and thicken, 



