292 MR. J. T. CUNNINGHAM ON THE [May 4, 
EXPLANATION OF THE PLATES. 
Puate XXVIII. 
Explanation of lettering: f, follicular epithelium; v.m, vitelline membrane ; 
zr, zona radiata; g.v, germinal vesicle; b.v, blood-vessels ; g.c, germinal 
cells; e, superficial germinal epithelium ; ¢, cells in interior of ovum; ¥, 
yolk-masses. 
Fig. 1. Ovum of Lepidosiren (Protopterus) before commencing formation of 
olk. 
- reo of Lepidosiren (Protopterus), to show the commencing formation 
of yolk. 
. Ovum, with cells in interior. 
. Nearly mature ovum, to show differentiation of yolk into a peripheral 
and central portion and modification of germinal vesicle. 
6. Two ova, belonging to the same series as fig. 3, to show the proli- 
ferating follicular cells. 
. Early stage in development of ovum, represented in figs. 3, 5, 6, to 
show the central mass of germinal cells which, at 2, have com- 
menced to fuse, and the invaginated mass of cells which form the 
follicular layer: 0, immature oyum belonging to series represented 
in figs. 1, 2, 4. 
to 
co 
oo 
? 
=~] 
Puate XXIX. 
Fig. 1. Germinal vesicle of ovum (Plate XXVIII. fig. 4), more highly mag- 
nified, to show its specialization into an outer and inner layer: 
m, germinal spots. 
2. A portion of ovum (Plate XXVIII. fig. 1), more highly magnified. 
3, Germinal vesicle of same ovum, highly magnified, superficial view : 
n, germinal spots. 
4. The same, in section; lettering as before. 
5. Portion of ovum a little more mature than that shown in Plate 
XXVIII. fig. 2. 
6. Nearly mature oyum. 
7. Less mature ovum of same series as last, to show the follicular epithe- 
lium resting directly upon the contents of the ovum; y, yolk- 
particles in follicular cells. 
8. Very young ovum. 
9-20. Cells from interior of ovum (Plate XXVIII. fig. 3), showing 
various conditions of division and degeneration: y', yolk-particles 
in interior of cell; 7, their nucleus; y, yolk of oyum. 
3. On the Mode of Attachment of the Ovum of Osmerus 
eperlanus. By J. T. Cunninenam, B.A., F.R.S.E., 
Fellow of University College, Oxford, and Superin- 
tendent of the Scottish Marine Station. (Communicated 
by Mr. F, E. Bepparp.) 
[Received April 20, 1886.] 
(Plate XXX.) 
In several works on Ichthyology and Pisciculture it is stated that 
the ovum of the Smelt is adhesive. The mode of attachment is 
described as differing from that which occurs in the Herring-ovum in 
the following manner :—In the Herring-ovum the whole of the outer 
surface of the egg-membrane at the moment of deposition is gluti- 
nous, aud the ovum becomes attached at any part of the surface 
