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Part III. — Eighth Annual Report 
Many spermatozoa are seen endeavouring to bore their way into the ovum 
at different points of its surface, and the heads of some at least have 
succeeded, as is shown by their disappearance into the vitelline membrane, 
while the vibratile tails project from the surface of the bounding 
membrane. The changes resulting inside the ovum are cloaked by the 
abundant deutoplasmic granules. Must of my observations were made on 
living ova, in which it is impossible to see the phenomena connected with 
fertilisation and the expulsion of the polar globule (PL V. fig. 4, p.g.). 
Moreover, in those ova which I fixed, stained, and mounted, the alterations 
were not visible. Whatever the changes may be that supervene on the 
union formed, the result is apparent in the subsequent activities of the 
coalesced products. 
The polar globule extruded by the ovum, so far as seen, is not stalked 
but sessile, and in many cases it persists till the oosphere has undergone 
repeated segmentation. When seen in the segmenting oosphere, though 
not distinctly stalked, it is generally ellipsoidal in shape. 
AVhile these changes are in progress, the ova, which on liberation have 
descended to the bottom of the glass aquaria, remain there unless stirred 
up, as it is advisable to do when the contents of the spermatic vessel are 
mixed with the water containing the ova. They rapidly settle again upon 
the bottom till they develop to a stage when they are clothed with cilia, 
and freely move about. 
A very marked feature in the active cell, in several fertilisations which 
were effected, was the great number of irregular changes simulating seg- 
mentation that took place. The protoplasmic contents were continually 
undergoing change, and the number of vesicles which were budded off and 
reabsorbed into the cell from which they arose was so varied, that within 
four hours upwards of SO distinct shapes were assumed by the cell or by 
the mass. Sometimes the periods of activity were intermittent, and rest- 
ing stages occurred during which no change in shape took place. During 
these resting stages, although the shape of the mass remained the same, 
there might be exhibited a regrouping of the contents of the cell and vesicles, 
but the regrouping was not so manifest as in the formation of the vesicles, 
when the protoplasmic flow into the vesicles was very apparent. The 
vesicles at first were colourless, but the deutoplasmic granules carried in 
the stream soon coloured them. A characteristic of such a cell was the 
smaller quantity of deutoplasmic granules present in it as compared with 
a normally segmenting cell. After a period of rest a fresh spurt of 
activity ensued, the coming changes being presaged by the clearing up of 
the cell contents at the point where the alteration was to take place. Though 
I watched a single changing cell of this character for a whole day, I never 
was able to ascertain whether any progressive development took place, 
or whether the alterations were a sign of pathogenetic forces at work. The 
result of several hours of change, with intervening resting stages, was that 
the object generally assumed the form of a single cell, indistinguishable 
from the cell from which the serial changes started. Undoubtedly some 
of the changes that took place are comparable with what Brooks * observed 
iu the American oyster, Ostrea virginica, but as I never found that the 
cell, which had exhibited this false segmentation, after it had returned to 
its original shape, underwent further development, I prefer to regard it as 
simulating segmentation, and not merely a departure from the normal type 
of segmentation which was now and again the case. The last exhibited 
progressive development and the segments differed only in their arrange- 
* "The Development of the Oyster, ,} Studies from Biological Laboratory of Johns 
Hopkins's University , 1880. 
