66 BULLETIN OF THE 
Within the “chorion” is the structureless vitelline membrane which 
closely invests the substance of the egg. It is thinner than the chorion, 
from which it is easily separable after maceration, This membrane in- 
vests mature eggs before they leave the ovarian follicle, and is doubtless 
a product of the vitellus itself. 
In making sections portions of these membranes were often cut. The 
vitelline membrane stains faintly in Borax carmine; the chorion retains 
its layer of outer granules, which are not dissolved in alcohol. There is, 
however, no trace of the areal arrangement of these granules, such as has 
been figured by Ludwig (’76) for Philodromus limbatus. 
The egg is composed of finely granular protoplasm, in which is accu- 
mulated a large amount of nutritive material in the form of albuminoid 
yolk corpuscles, and minute fat globules. The albuminoid material is so 
distributed as to give the protoplasm a characteristic arrangement. The 
latter consists of a central mass enveloping the nucleus, a peripheral 
layer, and a coarse network connecting the two, 
The peripheral layer (couche germinative of Balbiani) is the most strik- 
ing feature in the arrangement of the protoplasm. It is in immediate 
contact with the inner surface of the vitelline membrane, and is so 
crowded with fat globules that Balbiani concluded erroneously that it is 
composed exclusively of such globules. 
The central mass of protoplasm forms around the nucleus an irregu- 
larly limited, spheroidal envelope, containing neither yolk corpuscles nor 
the fatty globules which are so characteristic of the peripheral layer. Its 
outer portion is continuous with branching protoplasmic strands, which 
form a coarse network around the yolk corpuscles, 
According to the observations of Balbiani the ‘‘ yolk nucleus ” persists 
during a part, at least, of the embryonic development, and should there- 
fore be mentioned as one of the constituents of the egg. There is also to 
be included the perivitelline fluid, which makes its appearance during 
the contraction of the vitellus. I have no positive information concern- 
ing the source of this fluid, but having found no evidence of its existence 
in a definite morphological condition before the contraction takes place, 
I rest upon the assumption that up to this time it is uniformly distrib- 
uted through the formative portion of the vitellus. 
