Suberites domuncula, Nardo. 33 
present that spherical form which it would do if, as in other 
cases, it had been isolated in the midst of the sponge-tissue. 
Taking the elements of the ovum one by one from without 
inwards, it will be found to consist of a thick chitinous capsule 
followed by a delicate membrane filled with the yelk. The 
capsule, as before stated, is convex towards the sponge, flat 
towards the shell, and polygonal laterally, presenting on its 
convexity a great number of minute circular granules or 
points arranged more or less hexagonally, more or less pro- 
jecting beyond the surface, often possessing a punctum in the 
centre, and always connected with each other by a fold 
of the surface, so that it presents under high microscopic 
power a reticulated appearance (figs. 3, a, and 4). This part 
of the capsule is very thick when compared with the side 
towards the shell, being composed of five or more chitinous 
layers, amounting in all to 1-3000th inch, while the flat side 
hardly amounts to more than one of these layers. Interiorly 
it is smooth, where it is in contact with the delicate mem- 
brane investing the yelk, and appears to be uniformly closed 
on all sides; so that no aperture whatever could be detected 
in it. 
The yelk, on the other hand, surrounded by this “ delicate 
membrane,” which is hardly demonstrable from its trans- 
parency and thinness, consists of spherical refractive granules 
about 1-12000th inch in diameter, among which are a great 
many oil-globules and starch-granules, the latter of a greyish- 
white colour, more or less oval in form, flat, and presenting a 
crack-like translucency in the centre, varying in size under 
1-600th inch in diameter and becoming of the usual opaque 
blue colour under the influence of iodine, when they strikingly 
contrast with the whiteness of the yelk-granules generally, 
which do not become so coloured. 
Such is the composition of this ovigerous layer, and such 
the characters of the contents of the ova in every instance that 
I have examined ; so that it may fairly be assumed that under 
these circumstances none ever get beyond the granulation of 
the yelk in this position, whatever they may do afterwards 
when impregnation and the duplicative subdivision of the yelk 
destroys the individuality of the yelk-granules and leads on 
to the development of the embryo—a state which I have not 
witnessed, nor do I know where to find; but as the ovigerous 
layer is only to be seen over the surface of the hard objects 
enclosed by the Suberite so long as they exist, and no trace 
of such a layer or any ova can be discovered after the shell 
has disappeared, even when its mowld still remains empty, 
which is often the case (as proved by a specimen where the 
Ann. & Mag. N. Hist. Ser. 5. Vol, xii. 3 
