2 FOOT. [VoL. XII. 
identical structures. Stuhlmann distinguishes two kinds of 
Dotterkern: t.e.* Diffuse Dotterkerne,” that which is distributed 
throughout the cytoplasm (cf his Fig. 137 with my Fig. 4), and 
« Eigentlicher Dotterkern,” that which is aggregated at one of 
the poles. For examples of polar Dotterkern see Figs. 164, 165, 
at, 1X4 and examples:on Dat. XxX. 
In a recent paper by J. W. Hubbard! on the “ yolk-nucleus”’ 
in Cymatogaster, he clearly traces the “yolk-nucleus” from the 
germinal vesicle to one pole of the egg ,; and his figures show 
an aggregation of these granules fully as pronounced as either 
of the polar rings of Al/lolobophora foetida. 
Leydig’s? description of the granules (in the egg of Argulus), 
which aggregate at both poles of the egg, is strikingly suggestive 
of the polar rings. “In der Substanz des Spongioplasmas 
erscheinen jetzt auch wirkliche Granula oder dunkelrandige 
Kornchen, welche sich zu zwet Haufen an betden Polen des Ezes 
ansammeln”’ (p. 300). 
I am greatly indebted to Professor Wheeler for generously 
allowing me to study his AZyzostoma preparations, and provid- 
ing me with adult JM/yzostoma to prepare with Korschelt’s 
method. The study of these preparations has shown that in 
various tissue cells the cytoplasm can be differentiated into 
two distinct substances, one reacting to lithium carmine and 
the other to Lyon’s blue. 
It gives me pleasure to express my great obligation to Dr. 
Whitman for most kind and thorough criticism of my work. 
1 J. W. Hubbard, “The Yolk-nucleus in Cymatogaster aggregatus Gibbons.” 
Proceed. of the Amer. Philos. Society, vol. XX XIII, No. 144, 1894. 
Franz Leydig, “ Beitrige zur Kenntniss des thierischen Eies im unbefruchteten 
Zustande.” Zool. Jahr., Abth. f. Anat. u. Ontog., Bd. III, Hft. 2, 1888. 
