442 ELMER L. SHAFFER. 



of granular masses closely applied to the nuclear membrane, 

 and these masses grow in amount during the period in which 

 they are close to the nucleus. This is clearly shown in the early 

 works on the yolk-nucleus such as Munson ('99) in Lim-ulus, 

 Crampton ('99) in Molgula, Calkins ('95) in Lumbricus, Van 

 Bambeke ('95) in Scorpcena scrofa, Vander Stricht ('98) in the 

 human oocytes and in Tegnaria, and by others of the early 

 workers on these structures. In almost all these cases, the close 

 association of these granules with the nucleus and the similarities 

 in the staining reactions with that of the chromatin have given 

 the earlier workers the opinion that the granular masses represent 

 extruded nuclear material. In many of these cases, the granular 

 masses surround the centrosome forming a compact body with 

 sharp outlines. 



The formation of the typical yolk-nucleus (corps de Balbiani) 

 as found in the Arachnids has been described by Vander Stricht 

 ('98, '04) and Faure-Fremiet ('10). Here, as in other cases, the 

 granules (mitochondria) forming the yolk-nucleus are first found 

 in a perinuclear zone. Within this granular mass is found a 

 deeply-staining vesicle, and later the mitochondria gather about 

 it in concentric layers forming the typical compact Arachnid 

 yolk-nucleus, which usually shows a ray-like structure. The 

 relation between the yolk-nucleus and the attraction-sphere has 

 often been noted. I have previously called attention to the fact 

 that the mitochondria are usually (although not always) localized 

 at the pole of the cell at which the centrosome, sphere or idiozome 

 lies. In the formation of the compact Arachnid yolk-nucleus, 

 the mitochondria gather about the centrosome-sphere as a center, 

 the relation between the two being only spatial. Duesberg 

 ('12) has noted this relation and applies the term "idiozom" 

 or "centrotheka" to the central vesicle of the yolk-nucleus and 

 points to the fact that this conception corresponds to Henneguy's 

 definition of the "corps de Balbiani": " Un corpuscle centrale 

 entoure d'un zone d'aspect homogene on finement granuleux." 



It thus seems that in oocytes the perinuclear ring of mito- 

 chondria may behave in two ways; it may become dispersed in 

 the cytoplasm and give rise to yolk in the periphery of the cell 

 (as seems to be the case in the insects), or the mitochondria of the 



