ELMER L. SHAFFER. 



in the egg of Helix. R. Vander Stricht ('n) has described in the 

 oocyte of the cat a "couche vitellogene" or perinuclear ring of 

 mitochondria which grows in size during the early growth stages 

 of the oocyte and which later becomes dispersed toward the 

 periphery of the cytoplasm and there gives rise to yolk. O. 

 Vander Stricht ('94) has also described a "couche vitellogene" 

 (of mitochondrial nature) in the oocytes of the bat, which in the 

 young oocytes is arranged in the perinuclear zone, but in the older 

 oocytes it becomes diffused in the cytoplasm. This diffused 

 substance forms the " pseudochromosomes " of the oocytes of 

 the adult ovaries and from these are derived the yolk bodies. 

 Wildman ('13) has described two kinds of cytoplasmic inclusions 

 in the spermatocytes of Ascaris, the "karyochondria" and the 

 "plastochondria," both of which are derived from nuclear ma- 

 terial. The "karyochondria" become transformed into yolk 

 granules which later fuse to form the "refractive" body of the 

 spermatid. The "plastochondria" have a negative behavior 

 and take no part in spermiogenesis. Recently Gajewska ('19) 

 has described a perinuclear ring of mitochondria in the oocytes 

 of Triton and indicates the relation of this to yolk formation. 



I have cited only a few of the cases in which the mitochondria 

 appear to have a genetic relationship to yolk formation, and as 

 will be shown later, this relation is more general than is usually 

 supposed. The chemical processes involved in the transforma- 

 tion of mitochondria into yolk cannot involve complicated chem- 

 ical changes since the mitochondria themselves are of a phos- 

 pholipoid nature and closely allied chemically to yolk. 



(c) Discussion. In almost every work dealing with oogenesis 

 and the study of oocytes, mention is made of certain cytoplasmic 

 inclusions which are either of a granular, globular or filar nature, 

 or else assume larger proportions and appear as single compact 

 bodies. Various names have been applied to these structures, 

 such as "Dotterkern" or yolk-nucleus, yolk-matrix, "couche 

 vitellogene," "corps de Balbiani," pseudochromosomes, extruded 

 nucleoli, "zona plasmatica perinucleare," etc. In nearly all 

 these cases it will be noted that these special portions of the 

 cytoplasm are involved in the process of yolk elaboration, and I 

 shall attempt to point out some of the homologies existing be- 



