Volume XII. May, 1590. Number 1. 
JOURNAL 
OF 
MORPHOLOGY. 
YOLK-NUCLEUS AND POLAR RINGS. 
KATHARINE FOOT, Evanston, ILL. 
PoLar rings have been observed in Clepszne by Grube, 
Leuckart, Robin, and Whitman,! in Rhynchelmis, by Vej- 
dovsky,? and in Allolobophora foetida® by the author. 
In the present paper I hope to prove that the polar rings 
and the so-called yolk-nucleus are one and the same sub- 
stance, and that therefore the material which forms these 
structures is by no means confined to the three forms just 
mentioned. In the fall of 1894, I identified the granular 
masses of cytoplasm found in the ovarian egg with the polar 
rings of later stages, and traced the substance step by step 
during the growth of the maturing and fertilized egg; but the 
publication of this work was reserved to form part of a later 
paper on the maturation and fertilization of the egg of AJlo- 
lobophora foetida. 
1C. O. Whitman, “The Embryology of Clepsine.” Quart. Journ. of Micr. 
Scz.. vol. XVIII, 1878, p. 234. 
2 F. Vejdovsky, “ Entwicklungsgeschichtliche Untersuchungen.” Prag, 1892. 
8 “ Preliminary Note on the Maturation and Fertilization of the Egg of A//o- 
lobophora foetida. JOURNAL OF MORPHOLOGY, vol. IX, 1894. 
