No. 1.] YOLK-NUCLEUS AND POLAR RINGS. 3 
ovaries will appear entirely normal. Iam inclined to believe 
that the condition of the ovary in this respect depends upon 
the length of time that has elapsed since the ceasing of its 
functional activity. 
METHOD. 
The origin and formation of the polar rings were first traced 
by various methods, none of which, however, differentiated the 
substance from all other constituents of the cell. The fixa- 
tives used were chromo-acetic, corrosive sublimate, corrosive 
acetic, Hermann’s fluid, Hermann’s fluid followed by Merkel, 
Merkel’s fluid, osmic acid of various strengths, picro-acetic, 
Parenyi’s, Flemming’s, etc. The stains used were various 
haematoxylins, various carmines, and numerous anilins. While 
I was engaged in a systematic effort to find a stain that would 
differentiate the polar-ring substance from other constituents 
of the cell, the publication of Calkins’s results from his study 
of Lumbricus made it still more important for me to sub- 
stantiate my results by differential staining. The use of 
lithium carmine and Lyon’s blue was suggested to me by 
seeing some beautiful specimens of nerve tissue, prepared 
(under the direction of Dr. Patten) by Miss Lewis of Harvard 
University; and I am indebted to Dr. Patten for subsequent 
advice as to the use of the stains. Shortly afterwards I found 
that Korschelt ! in 1889, had used practically the same method 
(borax carmine and Lyon’s blue) to differentiate the yolk- 
nucleus (Dotterkern) of various insect eggs; and in spite of 
his beautiful results (clearly differentiating Dotterkern from 
chromatin), I find very few investigators who have repeated 
his method.? 
1 Korschelt, ‘‘ Beitrage zur Morphologie und Physiologie des Zellkernes. Zool. 
Jahro., Bd. IV, Hft. 1, 1889. 
2 Calkins seems to have tried Korschelt’s method, and he says of it: 
“ After borax carmine and Lyon’s blue the yolk-nucleus and chromatin had the 
bright red stain of the carmine.” In Allolobophora foetida the only eggs that do 
not give a constant reaction by this method are eggs in some stages of 
degeneration ; for example, the “ great yolk plates” (?) of Cut 1 deeply stain with 
carmine, and persistently retain the red after treatment with Lyon’s blue long 
enough to stain the degenerating cytoplasm deeply. 
