OiN" THE EOEMATION OE THE EGG IN THE ANNULOSA. 
603 
The macula increases in size nearly in proportion to the growth of the Purkinjean 
vesicle, and is single from the earliest stage observed up to the latest, but appears often 
to contain vacuola. 
In eggs xiT)th of an inch in diameter the Purkinjean vesicle is almost hidden by 
the dark opake yelk, whose globules are about of an inch in diameter. At 
this stage it scarcely differs, except in size, from its appearance when it first became 
nsible. 
After this the egg increases but little in diameter ; the yelk-globules, however, grow 
until they become about -g^^ths or iwoths of an inch in diameter, and the egg be- 
comes quite opake. At this stage I could, on applying pressure, see a clear space, 
which was probably the Purkinjean vesicle ; but it was so delicate, and the yelk-sub- 
stance was so \iscid, that I was never able to get a good view of it. Acetic acid 
darkened the yelk but slightly, and did not bring any vitelligenous bodies into view. 
It dissolves the Purkinjean vesicle and macula, as usual. Ammonia makes the whole 
ovary very pale, the macula imisible. It also causes the Purkinjean vesicle to disap- 
pear, but not so quickly. The epithelial nuclei are, if the ammonia is very dilute, 
rendered plainer than they were before. In mature eggs the yelk consists of at least 
three parts. 
1st. Yelk-globules from to of an inch in diameter, quite clear and 
transparent. 
2ndly. Yelk-sphemles from g-inrotli to g-fpjyths of an inch in diameter, and of a 
greenish hue. These are not so regularly round as the preceding, and have a look of 
solidity, while under pressure the globules quite lose their shape and run into one 
another. 
3rdly. A ’viscid substance in which the two first are imbedded. 
The spherules and globules are generally of the size indicated, but a good many 
depart considerably from the average. No trace of a Purkinjean vesicle was ever seen 
in the mature eggs. These are nearly spherical ; and when a number of them are con- 
tained in the body, it is difficult to make an incision without some of them coming 
immediately through it. This was the case with several females which I examined in 
the middle of August, and in one of which I found 400 ripe eggs, besides which there 
were a few which I did not count, and a great number in the ovary in all the previous 
stages. I presume therefore that at this period the ■walls of the ovary are exceedingly 
distended, and give -way directly they are touched by any sharp instrument. 
The female makes a little hollow ball of earth in which she deposits a number of 
eggs together. I found several of these in the glasses in which I kept these animals, 
while on the contrary the specimens kept in confinement by M. Fabee '*, did not lay 
any. I unfortunately omitted to isolate these eggs, or to watch for the moment of their 
hatching, and cannot, therefore, state in what form the young one leaves the egg. A 
few days after the eggs had been laid, however, I found a number of young Polydesmi 
* 'Loc. cit. p. 274. 
4 N 
MDCCCLXI. 
