Germ Cells of Leptinotarsa Signaticollis. 155 



and the large polygonal masses of acid-staining yolk are produced 

 in the meshes of the reticulum. In the mature egg, the reticulum 

 is represented by the cytoplasm of the interdeutoplasmic spaces. 



This reticular structure may not be present as such in the living 

 egg, but granting that it is an artifact resulting from re-agents 

 used in fixing, the structure is one that varies in size and form at 

 different periods in the development of the egg ; and thus may be 

 regarded as representing regions of varying chemical or physical 

 consistency in the living ovum, that indicate the paths of distribu- 

 tion of the food stream. 



Korschelt ('89) observed in the egg of Dytiscus marginalis 

 that the granules from the nurse cells enter the ovum and migrate 

 in a broad stream toward the nucleus, which actually exhibits 

 amoeboid movements, sending out pseudopodia-like processes 

 toward the granules. These form changes, which were observed 

 in both living and fixed material, are regarded as manifestations 

 of an attractive force exerted between the nucleus and the granules. 

 Somewhat similar processes were observed in the eggs of Carahus, 

 Bombus and Apis. 



I have not found such pronounced evidence of nuclear move- 

 ment in either the living or fixed egg of Leptinotarsa. Fig. 11 

 represents conditions comparable to what Korschelt has described 

 in Dytiscus, although the nucleus does not show any change in 

 form. However, the facts are such as to indicate the presence of 

 an attractive force of some sort, probably of a chemical nature, 

 between the nucleus and food stream. 



At the periphery of the mature egg and enclosing the yolk, is 

 found a narrow layer of protoplasm continuous with the inter- 

 deutoplasmic cytoplasm . Since the yolk is elaborated from within 

 out, being first formed in the center of the egg, it appears that the 

 outer layer of cytoplasm together with the reticular part represent 

 regions where the cytoplasm of the primordial germ cells has 

 remained undifferentiated. 



The evidence all goes to indicate that the substance of the food 

 stream is identical with what has been called the ''yolk nucleus" 

 by a large number of writers, (Stuhlmann '86, Jordan '93, Balbiani 

 '93, Calkins '95) in the eggs of spiders, myriapods, amphibia, 



