GERM CELLS IN THE ARTHROPODA 119 
There now ensues a period of activity during 
which a large number of ovarian tubules develop 
in the female and testicular follicles appear in the 
male. A number of much debated problems exist 
regarding the cellular elements within the ovaries 
and testes of insects — problems which are of con- 
siderable importance in any discussion of the germ- 
cell cycle. Put in the form of questions, two of these 
are with respect to the ovary: (1) Do the nurse 
cells originate from the odgonia, thus becoming 
abortive eggs, or are they of mesodermal parentage ? 
(2) Does amitotic nuclear division occur in nurse 
cells and odgonia ? 
The answers to these questions differ according to 
the species of insects studied, and, as usual, the ob- 
servations and interpretations of different investi- 
gators do not always agree. They can be answered 
with certainty in the case of JMuvastor. All of the 
odgonia in this form are direct descendants of the 
primordial germ cell; the nurse cells are of meso- 
dermal origin; and amitotic division occurs neither 
in the nurse cells nor in the ojgonia. The situation 
is quite different in chrysomelid beetles. The nurse 
cells in the ovaries of the potato beetle all seem to be 
of germ-cell origin. That the nurse cells which are 
derived from odgonia are abortive eggs is the general 
opinion of zodlogists. Convincing evidence for this 
view has recently been provided by De Winter 
(1913) from studies of the apterous insect, Podura 
aquatica. In this species the proportion of eggs and 
nurse cells which develop from the odcytes is about 
