A Comparative Study of the Structure and Origin of the Yolk Nucleus. 699 
have a complete yolk nucleus. Its appearance is therefore not due to 
the yolk nucleus.” 
Edier (25) saw two zones in fish eggs, the outer of which he called 
the “Rindenschicht”. 
Bambeke (7) found that the cytoplasm of the egg of Leuciscus, Ripo- 
campus, and Lota is divided into an inner zone and an outer zone. The 
division of the cytoplasm into two zones was also seen by Lancaster (47) 
in Molluscs. Will (94) found a ring around the germinal vesic-le in insects. 
van Bambeke (6) found a granulär zone surrounding the germinal 
vesicle in the fish. 
Of reptile eggs, LoYEz(öBb) says: “One sees around the germinal 
vesicle a clear zone which Sarasin (79) has compared to the latebra in 
birds. Nemec (66) found a ring partly enclosing the germinal vesicle in 
very young eggs of Mvriapods, as Bambeke (5) had done also in the spider’s 
egg. In the egg of fishes Scharff (80) figures a dark zone of granules 
surrounding the germinal vesicle. Such a dark granulär ring around the 
nucleus has been described also, in spermatogonia by Auerbach (1). 
Munson (61) saw a dark ring around the germinal vesicle of Limulus 
both in the living egg and in preserved material. Munson has also seen 
a clear zone around the germinal vesicle, and as the clear zone seems to 
precede the dark, he attributed it to the entrance of karyolymph into 
the cytoplasm. Cunningham (22) regarded the clear zone around the 
germinal vesicle of fish eggs as an artefact, Carnoy and Lebrun and 
Lubosch (57) attribute it to faulty fixation. Lams (52) shows in fig. 27 
a living oocvte with an outer granulär zone containing the “Masse vitello- 
gene” in which is the vitelline body with its central corpuscle. Around the 
germinal vesicle, he represents a nongranular fibrous zone. 
According to van Beneden (11), the deutoplasm may be intimately 
mixed with the cytoplasm, but also at times separatecl, and of different 
Constitution, as when produced as a secretion in special Organs, the vitel- 
logenes of Cestodes, Trematodes, Distomes, and Turbellarians. Since 
this secreted deutoplasm is some times a granulär mass of amorphous 
substances, sometimes composed of cells, it needs not mix at once 
with the protoplasm, but forms a ring in the center of which the real 
egg cell is found. 
Coste (19) compared the cicatricula of bird’s egg to the entire alecithal 
egg of lower animals, and recently Riddle (77) has attempted to show 
that yolk is deposited in layers as a precipitate from without. 
According to Beddard (10), the yolk in egg protoplasm is probably 
derived from the surrounding follicle cells. Munson (61) found in Limulus 
Archiv f. Zellforschung. YHI. 46 
