Germ Cells of Leptinotarsa Signaticollis. 159 



tiation of the nurse cells has already been noted, and consists in 

 the chromatin of the nuclei taking on a granular appearance, 

 whereas in the young ovocytes the chromatin is in the form of a 

 spireme. It has also been pointed out that the nurse cells 

 undergo mitotic division for some time after the ovogonia have 

 stopped dividing, but before the formation of the egg-string and 

 the beginning of the growth period, mitotic divisions cease in those 

 nurse cells situated next to the ovocytes. As these cells are the 

 first to be called upon to supply nutrition to the egg, they are the 

 first to take on the characteristic appearance of the nurse cells as 

 found in the adult (Fig. 11), The first step in this process is 

 brought about by the grouping of the cells into cyst-like structures, 

 as shown in Fig. 15. These elongated cysts of polynucleated 

 masses do not maintain their enormous size, but gradually break 

 up into smaller pieces, even into parts containing a single 

 nucleus, and therefore, morphologically equivalent to a single cell. 

 After the cysts have appeared, the epithelial cells are found in 

 the spaces between the cysts, where their relation to the latter is 

 the same as their relation to the primitive germ cells of early 

 stages (Figs. 4, 6, etc.). This similarity of relationship suggests 

 that the cells of each cyst are descended from a single mother 

 cell, and examination of intermediate stages bears out this idea. 

 In earlier stages as in Fig. 1 the definite relationship between germ 

 and epithelial cells does not exist. However, as development 

 continues each germ cell becomes surrounded by its own set of 

 epithelial cells bringing about the condition shown in Fig. 37, 

 which may be regarded as the first step in cyst formation. From 

 this point, the germ cells, or rather the nurse cells as they now may 

 be called, undergo amitotic divisons of the nuclei, and the result- 

 ing polynucleated mass remains enclosed by the epitheUal cells. 

 At first the lines of demarcation of the cysts are not sharp, but as 

 the spaces which develop between them widen, the cysts become 

 more rounded in outline and distinctly separated from one another 

 (Fig. 16, which is a transverse section of an ovariole throughthe 

 region of the nurse cells) . This process begins among the lower- 

 most nurse cells and gradually extends throughout the distal 

 portion of the egg chamber. As the cysts appear at the 



