Nutrition of the Ovum of Scolia Dubia. 139 



partecipino solo passivamente, lasciandosi divorare dell' oocyte per 

 via di fagocitosa." 



Fundamentally tlie writer's observations on the ovary of Scolia 

 dubia during the first phase of nutrition are in accord with the 

 findings of Giardina in the ovary of Dytiscus. The heavy walls 

 of the yolk ducts w^iich Giardina describes as being composed of a 

 series of granules were homogeneous structures in Scolia dubia. 

 Within the cytoplasmic core there were no traces of fibrillation, nor 

 could any differential stain be made of this part of the cytoplasm. 

 In these structural details Giardina's Dytiscus material differs from 

 the specimens of Scolia dubia. 



Giardina is content to establish the presence of a first phase of 

 nutrition. In Scolia dubia, as showm above, the two phases are dis- 

 tinct ; one occurs within the terminal chamber, the other involves 

 only the follicles. 



Giardina says that the origin of the yolk ducts is in the unsevered 

 protoplasm and cell membranes of the last differential cell-divisions 

 which result in the formation of a '^rosette" of nurse cells attached 

 to an ovum or oocyte. "L' origine delle connessioni tra 1' oocyte e 

 le cellule nutrici e da ricercasi nella gia noto origine del rosette." 

 Conditions in Scolia dubia indicate that this is a correct inter- 

 pretation. 



Conclusions. 



1. The terminal filament does not take part in the supply of 

 the primordial cells from which oocytes and nurse cells are differ- 

 entiated. 



2. The follicle epithelium is not directly concerned with the 

 nourishment of the ovum. 



3. Nuclei within a cytoplasm to which they are exotic may divide 

 amitotically. 



4. There are two clearly defined stages of nutrition of the egg. 



The writer is indebted to Prof. T. H. Tuttle for kindly interest 

 sho-wn and help given in the work which was done in his laboratory, 

 to the Biological Staff of Johns Hopkins University for the privilege 

 of using their library, and to Dr. L. O. Howard and Dr. F. H. 



