No. 2. ] ANURIDA MARITIMA. 249 
and the smaller, the female pronucleus, a round ellipse. Some 
of the eggs contain very small central masses; several showed, 
instead of any central mass, a small one about halfway to the 
centre, distinctly containing a small nucleus. These facts 
point to the following interpretation: when the sperm cell 
enters the egg (just when this occurs was not determined) 
there is practically no localized protoplasm present. Its en- 
trance presumably starts the transformation of yolk into proto- 
plasm. During the passage of the sperm cell to the centre of 
the egg the protoplasm gradually accumulates, until on its 
arrival there it is surrounded by a conspicuous amount. Here 
it remains stationary until the egg nucleus, having been trans- 
formed in its peripheral position into the female pronucleus, 
returns to the centre surrounded by a small mass of proto- 
plasm, the two nuclei eventually uniting to form the cleavage 
nucleus. 
Many of the unsegmented eggs apparently undergo a process 
of degeneration, the process consisting chiefly in the formation 
of a large number of oil globules, which are protruded between 
the surface of the egg and the membrane; these form large 
masses on the surface of the egg. It is probable that such 
eggs failed in fertilization, and are consequently degenerating. 
Sections show that the yolk material is undergoing pathologi- 
cal changes and becoming clear in spots. The external mem- 
brane adheres more closely to the surface than in the case of 
the normal egg. There is, moreover, no vitelline membrane 
present. Ona large number of normal eggs, so large a number 
as to suggest its constant presence, is a small raised spot, con- 
spicuous enough to be seen on the whole egg. In section this 
appears as an irregular protoplasmic mass with apparently no 
definite structure. It possibly represents the place of entrance 
of the sperm cell; for a time it remains visible, but is eventu- 
ally absorbed or otherwise disappears. The vitelline membrane 
offers no particular points of interest; it is very thin and reacts 
strongly to a protoplasmic stain; its color is nearly the same 
as the protoplasm of the outer surface of the egg. 
