SPERMATOGENESIS OF THE GALL-FLY. 37 



never sure that a cross-section includes all of the rods or that a 

 single rod has not been cut more than once. 



The spermatids formed by this division seem therefore to be 

 equal in size and chromatin content, and all of them develop 

 into spermatozoa. There is no evidence of a heterochromosome or 

 chromatoid body passing undivided into one of the spermatids. 



By the end of the second spermatocyte division all of the polar 

 bodies are detached and show signs of disintegration, fragments 

 being frequently seen in the intercellular spaces giving the ap- 

 pearance shown in Fig. i6. 



The relatively distinct outline of the chromosomes seen in this 

 last figure persists for but a short time and is completely lost in 

 the young spermatids. Figs. 17 and 18 are early stages in the 

 transformation of the spermatids into spermatozoa. 



Such in brief is an outline of the main features of development 

 of the germ cells in the male of Dryophanta from the growth 

 period to the spermatids. There is but one true maturation 

 division — that of the second spermatocyte. The first spermato- 

 cyte division is indicated by the pinching off of a small quantity 

 of chromatin-free cytoplasm which forms the so-called polar body. 



Discussion. 



Doncaster in his studies of the gametogenesis of the gall-fly, 

 Neuroterus lenticularis , arrived at certain conclusions which may 

 be considered at this point. This species of Hymenoptera has a 

 similar life-history to that of Dryophanta. Thus according to 

 Doncaster the female generation emerges in April from galls 

 formed during the preceding summer and immediately lays eggs 

 in oak buds (species?). Early in summer the galls appear from 

 which males and females emerge. After copulation the female 

 lays eggs in the tissues of young leaves at the side of a small vein. 

 From the galls resulting, females emerge in the following spring. 



As in Dryophanta, therefore, the fertilized eggs of the bisexual 

 generation develop into females; while the unfertilized eggs of 

 the female generation produce both males and females. 



Doncaster found that the first spermatocyte division is abor- 

 tive — a small portion of the cytoplasm being constricted off as the 

 polar body. This is followed by a resting stage which resembles 



