182 GERM-CELL CYCLE IN ANIMALS 



Buchner (1910a, 19106) had no difficulty in find- 

 ing the *'besondere Korper" of Elpatiewsky and in 

 tracing it during the cleavage stages. He claims that 

 it originates from the "accessory fertilization cell" 

 described by Stevens (1904) as degenerating after 

 the egg breaks away from the oviduct wall, and that 

 it is chromidial in nature and should therefore be 

 called "Keimbahnchromidien." Stevens (1910), 

 however, has carefully examined abundant material 

 from Sagitta elegans and S. bipunctata, and no connec- 

 tion between the "accessory fertilization cell" and 

 the "besondere Korper" could be traced, the latter 

 appearing for the first time at the stage when the 

 egg and sperm nuclei lie side by side in the middle 

 of the egg, thus confirming Elpatiewsky's conclusions. 

 She admits the possibility of the origin of the "be- 

 sondere Korper" from granules of the accessory 

 fertilization cell, provided this material loses its stain- 

 ing capacity for a period, and suggests also that the 

 granules of chromatin-like material extruded from 

 the nucleus of the egg during maturation may take 

 part in its formation. Miss Stevens also believes 

 with Elpatiewsky that the "besondere Korper" 

 divides unequally between the two daughter cells of 

 the primordial germ cell and that this is a differential 

 division. She was unable, however, to detect any 

 constant difference between either the cytoplasm or 

 the nuclei of oogonia and spermatogonia. It is 

 worthy of mention that Elpatiewsky (1910) believes 

 that the "besondere Korper" may originate "aus 

 dem achromatischen Kernkorper." 



