DR. W. H. RANSOM ON THE OVUM OE OSSEOUS EISHES. 
459 
In one instance, seven minutes after impregnation, the germinal disk was seen not yet 
fully concentrated, and as it presented full face I watched in vain for several minutes 
some of the granules at a short distance from its outer margin, to see their progress 
towards it. This attempt was often repeated with a like result. But as from the first 
moment there are slight contractions of the protoplasm, minute displacements of such 
granules, if observed, would not be conclusive evidence of a streaming movement. 
That such streaming does, however, take place is, I think, certain from the ultimate 
position in which the granular matter of the formative yelk is found, and I have fre- 
quently seen the granules of the cortex arranged in lines radially placed around the 
periphery of the then concentrating germinal disk. The germinal disk is visibly increased 
in bulk three minutes after fecundation, but I have no doubt that it begins to concen- 
trate much sooner ; it continues to increase until all but a very few scattered remnants 
of the formative yelk are collected, and it is complete some time before cleavage, for 
which it is the necessary preliminary. 
That the disappearance of the yellow droplets from the cortical layer is due to 
the action of the water which has entered into the breathing-chamber, is shown by the 
fact that not only does it begin near the micropyle where the water enters, but it pro- 
ceeds more slowly in eggs which are too scantily supplied with water. 
As the concentration of the formative yelk goes on, and the discus germinativus 
increases preparatory to cleavage, the accumulation of minute oil-granules distinct from 
the large reserve oil-drops at the under surface of the discus increases. 
When at various stages after impregnation the egg was ruptured, and the germinal 
disk in process of formation examined, which was done in various media, it was found 
to contain no additional structural elements beyond those in the discus proligerus before 
fecundation ; but the yellow droplets were very few in number, or absent altogether, 
unless in cases where the egg had been treated with too little water, in which cases they 
were numerous. The same vacuolation and pseudo cell-formation were seen as were met 
with in the matter of the formative yelk, but no true vesicles or cells. The mass is 
essentially granular with a clear matrix in very small proportion, and is somewhat more 
solid than before impregnation. 
The inner sac during these first stages appears to get thicker and firmer, at least it 
is more easy to observe ; it is adherent to the germinal disk, over the outer surface of 
which it passes, and of which it probably constitutes the clear matrix. 
c. Mode of effecting impregnation . — To ascertain the function of the micropyle, the 
following observations were made. 
I first sought to close it by gentle pressure, while allowing the spermatozooids to have 
free access to all other parts of the surface of the egg. This was done with the ani- 
malcule-cage, prepared as before described (p. 457), the depth of the cell being some- 
what less than the diameter of the egg. In this way a power of x 100 may be used, 
which enables one to follow the spermatozooids distinctly. 
Experiment 1. — An egg was so compressed that its micropyle which presented was 
