200 GERM-CELL CYCLE IN ANIMALS 
work of Ancel, using Helix arbustorum for his material. 
He confirms many of Ancel’s results, objects to others, 
and adds certain new observations. The germinal 
epithelium is considered by Buresch to be a syncy- 
tium containing both in young and old specimens 
three sorts of cells, indifferent cells, egg cells, and 
nurse cells. Likewise spermatogonia are present 
not only in young but also in fully developed her- 
maphroditic glands. This is contrary to Ancel’s idea 
of successive transformation. Buresch’s view is 
indicated in Fig. 59. Here the vertical row of circles 
represents the nuclei of the syncytial germinal epithe- 
lium, some of which, as at m, change to indifferent 
germ cells. These may pass into the lumen of the 
acinus as spermatogonia of the first order (Sg. D) 
and divide to form spermatogonia of the second order 
(Sg. IT) which grow into spermatocytes (Sc); sper- 
matozoa are derived from these in the usual manner. 
Other indifferent germ cells remain in the wall, as at 
w, and grow into odcytes, and a third class of cells 
become nurse cells (n). In Fig. 58, A is shown a 
nucleus of the germinal epithelium about 4 microns 
by 6 microns in size. During differentiation into an 
indifferent germ cell (Fig. 58, C) the chromatin forms 
a nucleolus, and both nucleus and nucleolus increase 
in size until the former reaches a diameter of about 7 
microns. Those indifferent germ cells that are to 
produce spermatozoa separate from the epithelium 
with a small amount of cytoplasm and fall into the 
lumen of the acinus as spermatogonia of the first 
order (Fig. 58, D). These divide to form spermato- 
