ox THE EOEIVIATIOX OE THE EOG IN THE ANNULOSA. 
619 
0. 'timscorum, and the oil-globules were small. None of the females bore egg-cases ; but 
it was perhaps too late in the season. 
ThYSAIS'OUEA. 
Petrohiiis maritimus . — In this interesting animal each of the ovaries consists of a 
tube running along the side of the abdomen, and giving off, on its inner side, seven 
short egg-tubes, which lie above the intestine. These latter, therefore, are fourteen in 
number ; and in the beginning of September, when I examined them, each tube gene- 
rally contained towards its lower end three egg-germs, in which a considerable deposition 
of yelk had taken place, and towards its free extremity from fifteen to twenty egg-germs 
in earlier stages of formation. 
The egg-tube is lined with epithelial cells, generally from y-^th to — o^oo th of an 
inch in diameter. Their nuclei are about of an inch in diameter, and very 
faint. Often, indeed, they can scarcely be perceived ; but, generally, when the tube had 
been lying some time in syrup they became tolerably plain. At the free end of the 
egg-tube are some solid-looking nuclei, about as large as the nuclei of the epithelial 
cells, and only difiering from them in being more distinct, and possessing granular 
contents. 
These nuclei are generally all about the same size ; sometimes, however, one or two 
are larger than usual ; and as this was the case in the first specimen I examined, I was in- 
clined to believe that the nuclei increased in size, and thus became the Purkinjean vesicles. 
As I was not able in other specimens, however, to find any nuclei in the process of 
becoming Purkinjean vesicles, this view requires confirmation, though it is supported 
by the analogy of other animals. 
Although in an unaltered condition the epithelial cells of the egg-tube are very faint, 
and often altogether imisible, yet if pure water be added and the syrup be removed, the 
cell-walls and the epithelial nuclei gradually become quite plain. Most of the cells are, 
from the apposition of their neighbours, irregular and somewhat angular in shape ; here 
and there, however, we see one quite round, and these can scarcely be distinguished 
from the youngest Purkinjean vesicles. In the latter, however, the nucleus looks rather 
more solid. The smallest Purkinjean vesicle which I saw was -gy^oths of an inch in 
diameter. 
The yelk of the young eggs appears to possess no vitelline membrane ; nor, though 
the boundary of it is perfectly distinct, has it any definite shape, but, apparently in con- 
sequence of the pressure put upon it by its neighbours, the outline which it assumes is 
very variable. As, however, it continually increases in size, it gradually comes to occupy 
the whole width of the egg-tube, and then assumes generally a more or less wedge-like 
shape, the Purkinjean vesicle occupying the thicker end. There are usually three or 
four egg-germs in this stage (Plate XVII. fig. 37). 
The two or three most advanced egg-germs approximated more or less to the form of 
the mature egg, and were darkened by the deposition of granules and small oil-globules. 
ilDCCCLXI. 4 p 
