DE. W. H. EANSOM ON THE OVUM OE OSSEOUS EISHES. 
4*55 
yielding on pressure but a very few free, not yet cohering eggs, mixed with some still 
within their ovisacs, and at 10 a.m. the next day, on pressure her spawn came out in the 
usual way, forming a flat zigzag band. 
The outer layer, or “ eikapsel,” has a consistence much like that of fresh fibrine, is 
much thicker than the dotted yelk-sac, and is characterized by a radial striation. The 
striae look like tubes, have a distinct double contour for each wall (Plate XYI. fig. 28), 
but are filled with a vacuolating material, and do not seem to convey anything, either 
fluid or solid, into or out of the egg. They are vertically set in a clear matrix, and 
terminate on the outer surface by expanded ends or mouths, arranged in a regular alter- 
nating order (Plate XYI. fig. 26). The surface of the outer layer is thrown into deli- 
cate folds, which radiate from the ends of the “ tubes,” and the aspect of these when 
viewed full face is seen in Plate XYI. fig. 31. I could not make out after very careful 
search, hexagonal outlines such as Muller has figured, having the ends of the “ tubes” 
placed in their centres. The appearance of a vertical section is shown in Plate XVI. 
fig. 27, which represents the point of junction of two eggs. At the free surface the 
profile view is crenated, the clear matrix forming lenticular elevations between the 
depressed expanded ends of the “tubes.” The outer layer is separable only by tearing 
from the yelk-sac, and does not leave a clean surface. The “ tubes ” at their inner termi- 
nation divide into branches like roots, and are in some way intimately adherent to the 
outside of the thick dotted yelk-sac (Plate XYI. figs. 29 & 30). They have no expanded 
funnel-shaped mouths at this inner termination, such as Muller has described. Here 
and there in the substance of the outer layer, very delicate connecting branches pass from 
one “ tube ” to the other. The clear matrix is delicately shaded, as if faintly granular 
on its outer surface, which under high powers is seen laminated concentrically, and is 
sufficiently elastic to turn inside out, when a minute segment is cut off it. Its central 
substance is so translucent as often to escape detection in these segments. The appear- 
ance described by Muller, of oil-granules passing along the “ tubes,” may possibly have 
been due to vacuolation in them. Be that as it may, I saw appearances capable of 
being so construed, in the tubes of segments which had been cut off the surface of the 
outer sac without touching the yelk-sac, so that it is certain nothing passed from the 
inside of the egg along them. 
In various ways I tried to make out whether any absorption of fluids took place along 
them, but always with a negative result ; for these experiments I used weak ammoniacal 
solution of carmine, solution of prussiate of potash, and then a salt of iron, and per- 
formed artificial impregnation in these fluids, that they might be present at the moment 
of the greatest inward current. The cleavage went on, the yelk-sac was dyed through- 
out, the clear matrix more so than the tubes, the germinal mass not at all after five 
hours. In short I satisfied myself that these tubes either do not at all serve for imbi- 
bition, or in a much smaller degree than the clear matrix, which has marked powers of 
absorption, swelling up so as very much to increase its thickness after long action of water 
and in various solutions. I also tried the unimpregnated egg with like results, after forty- 
MDCCCLXVII. 3 Q 
