MALE GERM CELLS IN NOTONECTA 63 



summary of which has ah'eady been pubhshed (Browne '10). 

 The present stud}' deals only with the growth stages and matura- 

 tion divisions, no attempt having been made to treat the later 

 stages which have been elaborately worked out by Pantel and 

 Sinety. 



II. MATERIAL AND TECHNIQUE 



The material, consisting of the three species already mentioned, 

 was collected during four summers at Woods Hole, Massachusetts. 

 These species differ considerably from one another in size, in 

 wing coloration and markings, and in other characters. N. 

 insulata is the largest, with brown wings usually marked with 

 two black bands. N. irrorata is slightly smaller, and its wings 

 are black, mottled more or less with brown. N. undulata, the 

 most common species, is considerably smaller than the other two 

 and the wing color varies from a pure white to a white with one, 

 two, or three black bands. In respect to germ cell production, 

 there are two types. In N. undulata, all the stages of the sper- 

 matogenesis occur in the adult and even in the very young larva 

 throughout the summer. In N. irrorata and N. insulata, during 

 the greater part of the summer, the testis of the adult and late 

 larva is filled with cells in the late growth stages, the younger, 

 cysts being empty except those at the very tip of the testis where 

 a few spermatogonia occur. For only about a week during the 

 summer are division stages found in these two species; after this 

 the testis is filled with spermatids and spermatozoa. Pantel and 

 Sinety have noted the same slow evolution of the germ cells in 

 N. glauca. Probably owing to this long period of growth, the 

 cells of N. irrorata and N. insulata are larger than those of N. 

 undulata. The great size of the cells coupled with the diagram- 

 matic clearness of the spindle fibers and asters make the material 

 exceptionally fine for the study of the maturation divisions. 

 The French authors find it otherwise for N. glauca, stating that 

 "La figure chromatique est d'un tj'pe malingre, dans les cineses 

 maturatives du Notonecta, et peu favorable a une analyse 

 detaillee des phenomenes morphologiques" (op. cit., p. 136). 



