THE EMBRYOLOGY OF THE HONEY BEE 243 



tioned. In the chrysomelid beetles true "paracytes" were not 

 found. Instead, there are found issuing from the cells of the 

 germ band — ectoderm, mesoderm, sex cells — small globular bodies 

 formed by the emission of chromatin from certain of the 

 nuclei of the tissues concerned. These bodies Friederichs calls 

 "paracytoids." After entering the yolk they disappear. In ap- 

 pearance they resemble so closely the chromatin spherules formed 

 by the degeneration of the nuclei of the (primary) yolk cells, that 

 they are not distinguishable from these, and the term "paracytoid" 

 is made to cover chromatin spherules from both sources. Both 

 are morever supposed to be identical in function, which is pre- 

 sumably that of assisting in the digestion and assimilation of 

 the yolk. In Meloc typical "paracytes" were found ; these later 

 degenerate in the yolk and form "paracytoids." 



The aggregation of the yolk cells beneath the wall of the mid- 

 intestine in embryos of the honey bee was noticed by Kowalevski 

 in 1871, but this condition, as well as the occurrence of nuclei in 

 the peripheral layer of protoplasm surrounding the yolk at earlier 

 stages, is found in a far more pronounced form in the mason bee, 

 Chalicodoma (Carriere and Burger, 1897). Burger's descrip- 

 tion is as follows (p. 358) : 



"The yolk cells also participate in the formation of the epi- 

 thelium of the mid-intestine. Not directly indeed, in the sense 

 of affording material for its construction, but in that they doubt- 

 less afford nourishment to the entoderm bands. 



"At the time of the appearance of the entoderm bands the yolk 

 cells at the periphery, regularly distributed and connected to- 

 gether, form a complete sac, or if you will, a primary mid- 

 intestinal epithelium. 



"If the series of sections, which are intended to elucidate the 

 development of the wall bee, ceased just after the time of the 

 breaking through of the mouth, one would be inclined to consider 

 seriously whether the yolk cells did not form the definitive epi- 

 thelium of the mid-intestine. Possessing other stages, it is how- 

 ever evident to us, that the nuclei of the yolk cells degenerate, 

 forming a crumbling mass, which is absorbed together with the 

 remaining yolk. In the oldest embryo which I have sectioned 

 the intestine is empty of yolk and also of every trace of yolk 

 cells and their nuclei." 



