of Edinburgh, Session 1885 - 86 . 
599 
of the polar threads may he seen. In sections of the polar region of 
such eggs, the plane of the sections being parallel to the longer 
axis of the egg, deep pits are seen in the follicular epithelium. 
These pits are expanded at the bottom, and reach nearly to the con- 
nective tissue layer of the follicle, only a thin layer of epithelium 
separating the cavity of the pit from the inner surface of the con- 
nective tissue. Corresponding to these pits are seen processes from 
the chorion ; there can he no doubt that in the fresh living condi- 
tion the processes entirely fill up the pits. The chorion itself is 
much thicker than in the stage previously described, the processes 
are directly continuous with it, and like it are, at least as seen 
with ordinary magnifying powers, homogeneous. The processes are 
quite solid, and the inner surface of the chorion turned towards the 
vitellus is as even as in the earlier stage. The micropyle is seen 
again at one pole of the egg, but its condition is a little different. 
It is open externally, but closed by a thin portion of the chorion 
internally. It still contains a cellular thread, but this thread is 
shrunken in size, and has now no connection with the follicular 
epithelium, the surface of which is unbroken above the micropyle. 
Without further evidence, I concluded that the further develop- 
ment of the egg consisted in the thickening of the chorion and the 
elongation of the threads, these processes being due apparently to 
the secretory activity of the follicular epithelium. The probability 
of this being the case is shown by the fact that both epithelium and 
chorion are much thicker at the poles than at the equatorial region 
of the ovarian eggs. I had no doubt that the follicle burst and 
allowed the escape of the egg enclosed in its chorion with the 
threads at the poles. But I was unable from the above facts to 
ascertain exactly how the follicle opened. I had seen bodies in the 
ovary of some specimens of Myxine which looked like aborted eggs, 
and had surmised that these were corpora lutea, but they were too 
degenerate to afford any evidence of the exact manner in which the 
ovum had escaped. But in December and January I found a 
female specimen of Myxine in the ovary of which were no large eggs, 
but a number of collapsed follicles, from which the ripe ova had 
evidently escaped quite recently ; examining these follicles I found 
that each possessed a slit-like aperture at one end, and thus the 
question of the escape of the ovum with its threads is elucidated. 
