420 FRANK R. LILLIE 
granules, which we shall name attachment granules, at the tip of 
the perforatorium embedded near the surface of the fertilization 
cone. In one ease (fig. 5 a) the perforatorium is seen to be double, 
a condition that I have also observed once in a preparation of 
spermatozoa alone. The perforatorium now stains very strongly. 
The spermatozo6n is now, therefore, actually anchored in the 
substance of the fertilization cone by the perforatorium and 
attachment granules noted above. I interpret the increased 
strength of stain in the perforatorium as due to the flow of sub- 
stance through it from the spermatozo6n to form the granules 
found at its tip in the fertilization cone. 
One can give only a more or less probable interpretation of 
these phenomena. The extreme delicacy of the perforatorium 
and the presence of a distal enlargement on it make it improbable 
that it bores through the membrane in a merely mechanical way; 
and the improbability is strengthened by the fact that the sper- 
matozo6n is absolutely immobile after attachment to the membrane. 
It seems probable, therefore, that the vitelline membrane is weak- 
ened at the point of application of the perforatorium, presumably 
by a fluid flowing through the perforatorium, though on account 
of its extreme delicacy it is impossible to be certain that the per- 
foratorium is tubular. The staining reaction and differentiation 
of the fertilization cone could then be explained by the assump- 
tion that it is affected by a fluid furnished by the spermatozo6n, 
and the appearance of the granules within the fertilization cone 
as due to inflow from the spermatozo6n through the perfora- 
torium. The mechanism of the spermatozo6n certainly appears 
more complex than we have hitherto suspected. I would assume, 
therefore, that the material of the head cap, forming a reservoir 
of material at the base of the perforatorium, functions in relation 
to penetration. 
b. Penetration. The actual penetration of the head of the 
spermatozoon 1s shown in figs. 6, 7 and 8, all taken from material 
preserved forty-eight and one-half minutes after insemination. 
The complex made up of the fertilization cone and the head of 
the spermatozo6n acts asa unit. The cone retreats into the inte- 
rior of the protoplasm and the head of the spermatozoén becomes 
