GERM CELLS IN THE ARTHROPOD A 125 



into ova, while the more distant germ cells become 

 nurse cells" (p. 147). My observations agree 

 with those of Wieman ; no definite relations nor 

 nuclear evidence were discovered during the differ- 

 entiation of the oogonia into oocytes and nurse cells. 

 The data available do not suggest any method of 

 differentiation not already proposed, and still leave 

 the question whether the nurse cells should be 

 regarded as abortive germ cells or true somatic 

 cells one of personal opinion. 



A study of cyst formation in the testis of the potato 

 beetle has revealed what seems to be a series of events 

 in the male germ-cell cycle parallel to that in the 

 females of Dytiscus, Carabus, and Cicindela, during 

 which the nurse cells are produced. There are in 

 Leptinotarsa two pairs of testes, one on either side of 

 the body. Each testis consists of a large number of 

 follicles radiating out from near the center. Figure 

 39 is a diagram of a longitudinal section made 

 from the testis of an old larva. At the lower end 

 is attached the sperm duct (s.d) which is con- 

 nected with a cavity (c) within the testis. Just 

 above this cavity is a region containing degenerating 

 cells ; above this region is a mass of spermatogonia 

 (sg) not yet within cysts ; and this mass is capped 

 by a small group of epithelial cells (t.c). The major 

 part of the testis is composed of radiating follicles 

 containing cysts of spermatogonia, spermatocytes, 

 or spermatozoa (cy) . 



In that region of the testis surrounding and under- 



