700 
J. P. Munson 
cases where yolklike substances secreted bv the bning cells of the ovarian 
tube accumulate outside the egg membrane after the latter is formed, 
and that it cannot be distiuguished from the granules of the cytoplasm 
of the egg. 
Kohlbrugge (43) gives as origin of yolk two kinds of elements, cyto- 
microsomes and karyosoraes from the germinal vesicle. He recognizes 
two zones of yolk formation — one at the periphery imder the influence 
of follicle cells, the other at the center under the influence of the germinal 
vesicle. 
Munson (61) expressed the opinion that besides substances that enter 
the egg from the outside, granules issue, like little drops from the living 
substance itself. He expresses the view that the inner dark zone is not 
an artefac-t, because both he and Giardixa (29) have seen it in the living 
egg. He maintains that it is a normal oceurrence, but agrees witli Hert- 
wig (34) when he maintains that it is not due to extruded nucleoli. 
Munson (64) Claims that the inner dark zone is due to the action of 
karyolymph on food entering the egg from outside — the first Step in 
assimilation or digestion. 
It has been maintained by "Will (94) of insects, by Fol of Ascidians, 
by Roule and Balbiani of Myriapods, that diverticula of the germinal 
vesicle containing chromatin are pinched off from the germinal vesicle 
and move to the periphery where tliey form the follicle cells. Later Will 
abandoned this view. 
The fact that His tried to explain these zones as the effect of in- 
wandering leucocytes has already been referred to. 
Experiments on infusoria have shown the importance of the nutritive 
function of the nucleus. RefeiTing to observations of Will, Blochmann, 
Schäfer and Leydig on the extrusion of nuelear fragments forming 
the yolk nucleus iii the cytoplasm, Henneguy (32) remarks that both he 
and Löwenthal (54) have seen in the young ovule of the cat a stainable 
eorpuscle resembling a nucleolus, leave the germinal vesicle. 
Sarasin (79) observing concentric rings in the cytoplasm of Lacerta 
concluded as did Riddle (77) that these are results of a periodicity in the 
growtli of the egg, corresponding to variations in the nutrition of the animal. 
The wellknown connection between the latebra and the germinal 
vesicle in the hen's egg, and the connection of these with the alternate 
zones of white and yellow yolk are suggestive. Lams (52) found the attrac- 
tion sphere in the center of a protoplasmie mass called masse vitellogene. 
The latter seems to correspond to what French writers call couche vitello- 
gene in birds. Loyez (53 b) has c-ompared this to the cytocenter described 
