SPERMATOGENESIS OF THE GALL-FLY. 39 



Returning now to Dryophanta I should like first to consider 

 the stage represented in Figs. 5 and 6, which I believe corresponds 

 to the second spermatocyte resting stage mentioned by Don- 

 caster in Neuroterus. The figures at first glance suggest the 

 synapsis stage of other insects, but in view of other facts it is 

 difficult to interpret the condition as a fusion of chromosomes. 

 Earlier stages such as the prophase shown in Fig. 4 display the 

 same number of chromosomes as appears in the second spermato- 

 cyte division, 12, which is assumed to be the haploid number 

 approximately. Since there is no evidence in Dryophanta of 

 an intra-nuclear division of these 12 chromosomes into two groups, 

 a true synapsis at this time would be equivalent to a second 

 "reduction." A more probable interpretation of this "looped 

 stage" and one that is warranted by a close study of the sections 

 is that the limbs of a loop are the halves of a chromosome that has 

 undergone a temporary and incomplete splitting. With the 

 next step in the process, the formation of the polar body, the 

 split disappears and the chromosomes have every appearance 

 of being single, solid rods (Figs. 7 and 8). The latter condition 

 might of course be brought about by breaking of the loops at the 

 middle, but in that event one would expect to find twice as many 

 single chromosomes as loops. Such is not the case, for the 

 number of unsplit chromosomes is the same as the number of 

 loops so far as could be determined. Reversing the seriation at 

 this point would of course change the interpretation offered here ; 

 but the main reason for placing the looped stage before the other, 

 as has been mentioned above, is that there is no evidence of 

 polar body formation at this time. And to this may be added 

 the fact that the outline of the cell at the looped stage as shown 

 in Fig. 6 represents an intermediate condition between that of 

 Fig. 4 in which there can be no question about polar bodies being 

 absent, and Figs. 7 and 8, in which the polar bodies certainly are 

 present. 



An actual resting stage, if one occurs at this time, must be of 

 very short duration. The second spermatocyte division follows 

 very quickly after the formation of the polar body. Fig. 9 

 represents a prophase of this division in which the chromosomes 

 are surrounded by an Intact nuclear membrane. The spindle 



