GROWril AND DIFFER EXr I ATIGN OF THE GERM-CELLS 



157 



most, if not in all, cases breaks up into smaller and smaller fragments 

 which contribute, directly or indirectly, to the cytoplasmic growth. 

 In all these cases the history of the yolk-nucleus is such as to indi- 

 cate the participation of the nucleus in its formation. Calkins ('95) 

 endeavours to show that the yolk-nucleus in Lwnbriciis is directly 

 derived from the nucleus by a casting out of a portion of the chro- 



yn 



\<^ ^ 



Wi\ 



■^ 



C 





/ 



Fig. 80.— Vn'k-nucleus in earthworm, spider, and ascidian. [.4, B, CM. KINS; L-E, VAN 

 Bambeke; /"-/. Crampton.] 



A. Earl V ovarian egg of Z:?»«^W««. B. Later stage; fragmentation of yolk-nucleus. C. Ova- 

 rian egg of Pholcits. D. Later stage; disintegration of yolk-nucleus. E. Remains of the yolk- 

 nucleus scattered through the cvtoplasm. E- Early Stage of yolk-nucleus in Molgiila. G-L Dis- 

 integration of the volk-nucleus and enlargement of the products to form deutoplasm-spheres. 



matin-reticulum — a result agreeing in principle with earlier obser- 

 vations on other eggs by Balbiani, Henneguy, Leydig, Will, and 

 other observers. This conclusion rests partly on the apparent direct 

 continuity of yolk-nucleus and chromatin, partly on the staining- 

 reactions. Thus when treated with the Biondi-Ehrlich mixture (basic 

 methvl-green, acid red fuchsin), the yolk-nucleus at first stains green 

 like the chrohiatin, while the cytoplasm is red, and this is the case 



