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 oogonia, thus becoming 

 abortive eggs, or are they of mesodermal parentage ? 

 (2) Does amitotic nuclear division occur in nurse 

 cells and oogonia ? 



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 Miastor. All of the 

 oogonia 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 oogonia. 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 oogonia are abortive eggs is the general 

 opinion of zoologists. 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 oocytes is about 



