GERM CELLS IN THE ARTHROPODA 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 odgonia into oécytes 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 (¢.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- 
