ox THE EOEMATIOX OF THE EGG IX THE AXXULOSA. 
605 
The cells constituting the wall of the follicles are transparent, and vary in size from 
- g o^o ~o ths to of i^oh in diameter. Their nuclei are distinct, and from -g-^^ths 
to go^o o ths of an inch in size. Sometimes the cells are almost invisible, and the nuclei 
only can be seen. 
In eggs rather more advanced, a certain quantity of clear yelk may be seen round the 
Purkinjean vesicle, and the macula consists of about seven bright, solid-looking bodies, 
each measuring about -^ooth of an inch in diameter. The diameter of the Purkinjean 
vesicle is at first about half as large as that of the follicle in which it is contained, but 
increases in size much more slowly than the latter. A^Tien the follicle is about ^J^th 
of an inch in diameter, the yelk begins to become dark from the deposition of granules, 
which are very minute, none exceeding -g-^^th of an inch in size. In the mean time 
the maculae have become smaller and more numerous, until in the largest Purkinjean 
vesicles there are a great many of them, and they are very minute. 
This gradual increase in the number and diminution in the size of the maculae 
occurred in all but one of the specimens examined by me. In this case many eggs, 
even among those which had begun to darken, contained a large macula, generally sur- 
rounded by smaller ones. 
A gi'eat many of the eggs contained a vesicle (Plate XVI. figs. II, 12, &c.) like that 
of Arthj'onomalus, but much smaller and with no distinct nuclei. This small vesicle 
could by no means always be seen; and even in those ovaries in which it was most 
distinctly \isible, it appeared to be present only for a short time. It seemed to be 
succeeded by a small patch, like that akeady described as occurring in lulus. It is not 
seen in eggs less than y^th of an inch in diameter, and it can no longer be distinguished 
when the yelk has become quite opake. In one specimen out of twenty-six egg-folli- 
cles, larger than the above size and yet not opake, I saw it in eighteen, but in other 
specimens it was less constant, or even perhaps altogether absent. I have several times 
been inclined to look upon it as a mere accidental agglomeration of yelk ; but it is, I 
think, too regular and too constantly present. All that I have said about the “patch” 
in lulus, applies equally well to that of LWiobius. 
When the egg has attained a size of T^-oth to ^si’d of an inch, it has become quite 
opake, and without compression its contents cannot be distinguished. The yelk con- 
sists of oil 1-globules, varying from -ymroth of an inch down to a very minute size, and 
imbedded in a clear, sticky substance. On applying pressure the germinal vesicle at 
once comes into sight. It is ^-g- o o ths of an inch in diameter, and shows no trace of any 
nucleus, but appears to contain a clear fluid, with minute granules. 
At this stage the yelk seems to be surrounded by a delicate membrane, which, when 
the egg is mature, has become a strong shell. In eggs of this size it often happened 
that on applying pressure a second clear space appeared, always detached from, and 
three or four times as large as, the Purkinjean vesicle. This appeared to be a portion 
of the yelk free from the globules and granules ; it had no definite outline, and gene- 
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