DR. W. H. RANSOM ON THE OVUM OF OSSEOUS FISHES. 
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c. The acid reaction. — I sought in vain to isolate the acid of the yelk. In precipi- 
tating the albumen b by water, the supernatant fluid becomes acid, and the precipitate 
itself is so, until it commences to decompose. 
The acid, whatever it may be, is insoluble in alcohol, soluble in water, and forms a 
non-crystallizable soluble salt with baryta, which remains in solution in the alkaline 
reacting fluid, after the phosphates and sulphates have fallen, and is not precipitated 
from it by carbonic acid, but is by ammonia ; when dried and burned, it chars, and leaves 
an alkaline ash. It is, I believe, a compound into which phosphoric acid and an organic 
substance enter as constituents. 
A substance much resembling leucin was found among the alcoholic extractives of 
the yelk. 
The Grayling (Thymallus vulgaris). 
The ripe ova resemble those of trout and salmon in all essential particulars. 
The Pike (Esox lucius). 
The ripe ova have a general structure, essentially the same as that of Gasterosteus ; 
the inner sac is particularly easy to demonstrate, and may be separated, teazed with a 
needle, and mounted. The yelk-sac is covered externally by a thin layer quite struc- 
tureless under a power of X400, the equivalent of the “ eikapsel” in Perch. It is 
visible only in moderated light, at least with the lower powers, and then requires, in 
order to distinguish it from a diffraction effect, that note be taken of the flow of fluids, 
and the position of solid particles on its surface. 
It is this layer which causes freshly expressed eggs to adhere to each other and to the 
dish when in water. They do not thus adhere in air. Yelk-sacs long digested -in a 
weak ammoniacal solution of carmine become rather friable, but the homogeneous outer 
layer retains its plasticity, and on rupture by pressure may be seen stretched across the 
gaping fissures of the yelk-sac, tinged faintly with the dye, but quite structureless under 
a power of X 400, and careful illumination. 
The micropyle may be sought for in the same way as in trout eggs. The aperture 
at the apex is easily seen under a power of X 200 in full face. When the pit is viewed 
in f face with oblique light, it seems to have a trumpet-shaped tube, standing erect from 
the bottom of it (Plate XYI. fig. 25). This appearance is due to the fact that in a 
strong illumination the clear, colourless, outer layer is quite invisible, and the trumpet- 
shaped tube appearing to stand erect and unsupported, is the thick wall of the canal, 
which penetrates the outer layer, where it dips into the pit of the micropyle. 
The Puffe (Acerina vulgaris). 
The general structure of the ripe egg is the same as in Gasterosteics. The oil, 
however, forms but one large drop, the inner sac seems thicker, and the yelk-sac has an 
outer layer or “ eikapsel.” Eggs expressed from the parent may be manipulated with 
care if no water be added, as although very soft they do not adhere strongly ; but if 
