A Comparative Study of the Structure and Origin of the Yolk Nucleus. 671 
and its discharge into the ovarian tube. In the youngest eggs he showcd 
the presence of archoplasm containing a ccntrosome ; and traced the 
same through the ovarian history of the egg. Besides an attraction sphere 
and centrosome often forming a real aster, he showed the presence in the 
cytoplasm of amorphous masses resembling nuclei, which he designated 
as yolk nnclei reserving the name vitelline body for the egg attraction 
sphere. • 
In 1898 Bambeke (8) gave us an account of an elongated mass in the 
cytoplasm of the egg of Pholcus, staining deeply and partly surrounding 
the germinal vesicle as a ring or as a stainable band of substance near the 
periphery. Judging from his plates tliis corresponds to what I have called 
metaplasm in the egg of the tortoise. 
In recent years, contributions to the subject have been numerons, 
and some of them of considerable importance, notwithstanding the fact 
that so rhuch attention has been given to study of chromosomes. 
It appears from the literature thus far considered, that the term 
yolk nucleus includes many dissimilar things in the cytoplasm. Says 
Stuhlmann (86) of eggs of Hymenoptera: “Here is therefore two 
entirely different kinds of yolk nuclei — “Denn als Dotterkern be- 
zeichnen wir doch ein Gebilde, das von dem übrigen, normalen Dotter 
ab weicht.” 
Wilson (95) in his work on the “Cell in Development and Inheritance” 
even goes so far as to speak of the yolk bodies in the egg of the newt, as 
yolk nuclei. 
In 1900, Bouin (14) describcd, in egg of Bana, a dense mass in the 
cytoplasm attached to the germinal vesicle. In ovocytes he found it in 
form of crescent in which a central stainable granule could be seen. 
In the same year Gurwitch (31) published an account of his investiga- 
tions on the yolk nucleus in mammalian ova finding it always present in 
these eggs. 
Winiwarter (96) published a paper in the same year on the yolk 
nucleus in the mammalian ovum. 
In 1903 Skrobansky (85) figured and describcd the vitelline body 
in the human ovum and also in the cat. 
In the egg of Montis religiosa, Giardina (29) found in 1904, near 
the germinal vesicle a dense mass in the cytoplasm at the point where 
chromatin is massed in synapsis, and in the center of this mass were stain- 
able granulös. 
Interesting studies on the yolk nucleus in eggs of birds and mammals 
were published by Holländer (36) in 1904. 
