Germ Cells of Leptinotarsa Signaticollis. 195 



especially in the region of the terminal thread, becomes invested 

 with striated muscle fibers, the whole being inserted in the dorsal 

 wall of the body. 



There is no evidence of a chromosome basis for the differentia- 

 tion of functional germ cells from nurse cells. On the other hand 

 the production of a semi-fluid medium from the interaction of 

 epithelial and ovariole stalk cells, at the time when the differen- 

 tiation is occuring, suggests that it is an important factor in the 

 process. Those of the primordial germ cells coming under its 

 influence are enabled to develop into functional ova ; the remainder 

 become nurse cells. 



Mitotic division figures disappear first among the germ cells 

 of the ovariole at its lower proximal end, but they can be seen 

 for some time afterward in the more distal part among the poten- 

 tial nurse cells. The persistence of the mitotic divisions in the 

 latter instance suggests that the energy which is conserved in the 

 functional germ cells for the needs of developmental processes 

 is here being expended in cell divisions. The frequent occurrence 

 of multipolar and abnormally large single spindles is also noted. 

 Mitotic figures are never seen inside of cysts in the ovariole. 



The chromatin of the nuclei of the nurse cells appears more 

 highly granular than that of the germ cells; and this is the first 

 obvious result or accompaniment of the process of differentiation 

 of the nurse cells. Amitosis and formation of cysts takes place first 

 among those nurse cells at the base of the chamber and adjacent 

 to the functional ova. The contents of each cyst are the descend- 

 ants of a single mother cell. At first, only the nucleus divides; the 

 result being large polynucleated masses. Later the division extends 

 to the cytoplasm, producing in some cases mononucleated masses 

 morphologically equivalent to single cells. Amitosis is regarded 

 as an indication of an intense metabolic activity involved in 

 the differentiation of the nurse cells which demands the most 

 rapid and expedient method of nuclear division. This is in accord- 

 ance with the view taken that amitosis represents a more primi- 

 tive and relatively simpler method of cell multiplication than mito- 

 sis. 



The prolonged amitotic period brings on certain chemical 



