252 GERM-CELL CYCLE IN ANIMALS 
this is the pachytene stage. The filaments then 
begin to unravel (Fig. 62, 6-7), become distributed 
Fic. 62.— Prophases of the heterotype division in the male Axolotl. 
1, nucleus of spermogonium, or young spermocyte; 2, early lepto- 
tene; 3, transition to synaptene; 4, synaptene with the double 
filaments converging towards the centrosome; 4, 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, 
