696 
J. P. Munson 
did not suspect that the yolk nucleus lias its origin in cells, entering the 
egg from without. The question of the origin of the yolk nucleus was not 
eonsidered seriously at that time, as the problem of the centrosome did 
not then exist. 
There is no doubt that egg cells are nourished by other cells, but 
how far such cells can destroy the unity of the egg or how far they in- 
fluence the polarity of the egg, is a matter deserving more attention than 
it has received. Munson (65) has shown that in Limulus the position 
of the yolk nucleus bears no c-onstant relation to the point of attachment 
of the egg, where the granulär food material secreted by the lining epithelial 
cells of the ovarian tubes, accumulates. 
In Myzostoma, according to Wheeler (98), the ovarian egg is aceom- 
panied by nurse cells which fuse at opposite poles of the egg, and give 
rise to a spongy protoplasm corresponding to the vegetative and the 
animal pole of the egg. 
That eggs may resemble amoebae and devour other cells as protozoa 
do, seems to be pretty well established. Weismann tries to explain the 
need of this on the grounds that the nourishment received from the blood 
is insufficient. The eggs may grow to a certain size from that source alone, 
but to grow larger, they devour the smaller cells around them. In Dapli- 
nids, according to Weismann (90), the food cells may first dissolve into 
a Protoplasmalösung which then is devoured by neighboring cells, and they 
in turn dissolve, vielding their substance to the growing egg. 
Degenerative Processes. 
While the entrance of cells may be eonsidered normal in many cases, 
there is no doubt that it is in many cases a result of degeneration of the 
egg; and, unless degeneration be eonsidered a normal process, must be 
regarded as pathological. 
According to Weismann (90), the eggs of Daphnids undergo spon- 
taneous degeneration, and are sometimes absorbed by neighboring 
epithelial cells. In 1849 Leydig (50) described degenerative eggs. He 
says: “Außer den so also veränderten primitiven Eiern trifft man aber 
in demselben Eierstocke auch viele Eier, die eine wohl rückgängige Meta- 
morphose anfangen.” 
Will (94) described in insect eggs, wandering cells which he assumed 
to be food cells, but two years later he interpreted this as the beginning 
degeneration of eggs that liave not been diseharged. 
Wagner ( 89b) speaking of the dog’s ovary says: “Die ungeheure 
Zahl von Eiern wird durch das Zugrundegehen einer Menge derselben 
