2OO EDMUND B. WILSON. 



for study, and the diagrammatic clearness with which the chromo- 

 somes appear in many of the sections precludes, I' think, the 

 possibility of error in respect to the number. 



In my description of the male groups I emphasized the fact 

 that the two components of the " accessory " are of slightly un- 



88 



*> AA** 



FIG. i. a, b, Syromastes marginatus L., spermatogonial chromosome- 

 groups ; c, d, ovarian groups of the same ; e, f, Pyrrochoris apterus L., ovarian 

 chromosome-groups. 



equal size (as is shown in the photographs accompanying the 

 paper), and that they are recognizable in the spermatogonial 

 groups as two separate chromosomes which are the second and 

 third smallest of all the chromosomes. In the female groups 

 each of these chromosomes is represented by a corresponding pair 

 (black in the figures). In most of the ovarian groups the smaller 

 two are readily recognizable, and in some cases, though not al- 

 ways, this is also true of the larger pair. The numerical and 

 size-relations are such as to show that after maturation the egg 

 must contain one member of each of these pairs. Though noth- 

 ing is directly known of the maturation-process in the female, it 

 may be inferred with probability that in synapsis the two larger 

 and the two smaller of these pairs unite to form two correspond- 

 ing bivalents, which may be designated as aa and bb (II and ii. 



