598 
Proceedings of the Boyal Society 
description of some ripe ova found in a female Myxine sent to the 
Copenhagen Museum in the month of September 1862. He also 
compares the envelope of the ovum with its polar threads to the 
capsule of the deposited ovum in Elasmobranchs. The ova were 
lying at the edge of the ovary, to which they were only connected 
by the entangling of the threads. In the woodcut to Steenstrup’s 
paper one of the eggs has the polar portion of the capsule at one 
end detached like an operculum. 
I have recently, by cutting sections of very large ovarian eggs of 
Myxine, ascertained that the envelope of the deposited egg is 
developed entirely within the follicle. It is usual to distinguish 
primary egg membranes as chorion or vitelline membrane, according 
as they are developed by secretion from the follicular epithelium, or 
from the ovum. I am inclined to think that in this sense the 
envelope of the Myxine egg is a chorion, but I have not yet com- 
pletely examined the question of the development of the membrane 
in all details. The important point is that the envelope is a primary 
egg membrane, and that the threads are solid processes from it. In 
sections of the polar region of ovarian eggs about 19 mm. in length, 
the ovum is surrounded by three distinct layers, corresponding to 
those universally found in vertebrate ovaries. The most external 
is the connective tissue layer, which is of considerable thickness, 
and is continuous with the thin mesoarium. Next to this is the 
follicular epithelium, composed of several layers of elongated cells, 
arranged with their long axes perpendicular to the surface of the 
ovum. Next is the egg-membrane, which is homogeneous, and 
forms the sole envelope of the deposited ovum. At one pole is 
found a cellular process projecting from the follicular epithelium, 
and penetrating through the chorion. Thus a canal is formed in 
the latter, constituting the micropyle. But this aperture is not at 
this stage open internally ; the micropyle penetrates nearly, but not 
quite, to the inner surface of the chorion. 
In the vitellus, close beneath the inner end of the micropyle, is 
seen the germinal vesicle, which is globular, large, and distinct. In 
my preparations nucleoli could not be made out, but from its 
appearance the vesicle did not seem to have undergone much change 
from its original condition. 
In older eggs, about 21 mm. long, the beginning of the formation 
