692 
J. P. Munson 
genesis adds a new impetus to speculation as to the probable meaning 
of the yolk nucleus. It was then suspected that parthenogenesis in aphids, 
depends upon it. Balbiani suggested that the foUicle cells, penetrating 
the egg, act as a Spermatozoon, the presence of the yolk nucleus in inseet 
eggs being evidence of such a follicle cell in the egg. Balbiani (3) claimed 
to have seen the follicle cells in the egg of the c-at. He says: “La vesicule 
embryogene nait par bourgeonnement de l’une des cellules epitheliales 
qui entourent l’oeuf dans le follicule de Graaf.” To strengthen his 
argument he quotes Pflüger and Lendgren who claimed to have seen 
cells passing through the zona radiata of the cat. Balbiani (4) gives 
figures showing in one a large yolk nucleus lying at the periphery of the 
egg, close to the follicle ; and in another figure, he shows how this supposed 
cell has entered the egg, leaving behind it a path or canal. He shows 
the same in the egg of GepJiilus, where a large nucleus connected with 
the follicle has pushed in the outer protoplasm of the egg, and developed 
around it a rudimentary aster. 
In the egg of spiders, where there is no follicle, Balbiani claimed that 
the yolk nucleus is due to the entrance of a cell of the egg stalk. He 
claimed with v. Wittich, that the yolk nucleus in spiders is first seen in 
the neighborhood of the stalk. The writer has investigated this question, 
and finds that both were mistaken in these observations. Munson (61) 
has also shown that in Limulus, whose ovary resembles that of the spider, 
there is no constant relation between the position of the vitelline body 
and the point of attaehment of the egg, not even in the earliest stages of 
the egg. Munson has also figured a yolk nucleus attached to the periphery 
of the egg by a band of fibrous protoplasm; but it shows no Connection 
with the stalk, and is given no such interpretation. 
In connection with the above theorv of Balbiani it is of some interest 
to recall the socalled paracopulation cells of eggs of Daphnids described 
by Weismann and Ischikawa (92). These investigators found that, in 
those eggs which are parthenogenetic, only one polar body is given off; 
while, in those that require fertilization, two polar bodies are extruded. 
In the fertilizable winter eggs, of six speeies of Daphnids, belonging to 
four genera, there is found, in the egg during ovarian development, a cell 
which like a foreign intruder moves slowly about. It arises, according to 
them, from extrusion of nuelear substances into the body of the egg cell, 
develops into a real paranucleus, and finally becomes surrounded by a 
cell body. 
The subsequent history of this cell is that it fuses with one of the 
cleavage cells after development has begun. They claim that this is com- 
