STUDIES OF FERTILIZATION 363 
gonal areas with the eggs in the centers of the hexagons (fig. A). 
The substance that sweeps the spermatozoa away from the sur- 
face of the eggs is the jelly. Synchronously with its formation, 
the alveoli of the cortical layer are emptied and the alveolar walls 
now appear as delicate lines crossing a wide perivitelline space! 
(fig. B). 
However, not all of the spermatozoa are thus carried out by the 
secreted jelly, but in the case of each egg a single spermatozoon 
remains attached to the vitelline membrane. This is very pret- 
tily demonstrated if the eggs are under some pressure, so that 
Fig. A. Diagram of fertilization with excess of sperm. The outflow of jelly 
from the eggs has carried the supernumerary spermatozoa away from the surface 
of the eggs (see text). In the case of each egg the single effective spermatozoon 
remains attached. From a sketch of the living object. 
the spermatozoa are prevented from reaching the eggs above or 
below. In this case one can discover the single spermatozoon 
attached to the vitelline membrane in practically every egg (fig. A). 
All stages of the disappearance of the cortical layer may be 
readily and rapidly observed. The alveolar walls, however, 
1Wilson (’92) states that ‘“‘from twenty to thirty minutes after fertilization the 
striae of the zona suddenly become indistinct and in the course of two or three 
minutes the zona itself entirely disappears, leaving only the outer membrane.’’ 
But inasmuch as he was under the impression that the unfertilized eggs possess a 
transparent, thick, gelatinous envelope like the fertilized ones, he failed to observe 
the interesting phenomenon of formation of the jelly described here. 
JOURNAL OF MORPHOLOGY, vol. 22, NO. 2 
