5i8 



Edmund B. Wilson. 



Figure 2. 



Anasa tristis. — a, Contraction-phase of synaptic period, showing "accessory" (A) and plasmosome (p); 

 h, spermatocyte-nucleus, late growth-period, beginning of the condensation, showing "accessory'' Qi) 

 and the w-chromosomes (m); c, a slightly later stage than the last; d, later stage, immediately before 

 the final condensation, from a long-extracted preparation; e, /, two sections of one nucleus, show- 

 ing all of the twelve chromosomes immediately before the disappearance of the nuclear membrane; 

 g, view of one pole of the late prophase just after disappearance of the nuclear membrane, the w-chro- 

 mosomes still wide apart; h, early metaphase-group in side view, showing approach of the m-chromo- 

 somes; /", four chromosomes from the metaphase, conjugation of the ra-chromosomes to form the small 

 central bivalent; j, early anaphase, separation of the m-chromosomes, "accessory'' at the left; k, polar 

 view of metaphase-group, first division; /, polar view of metaphase-group, second division; m, n, 

 anaphases of second division, showing division of wj-chromosomes and the undivided heterotropic 

 chromosome; o, p, spermatogonial metaphase-groups drawn as carefully as possible to show sizes of 

 the chromosomes. 



