Composition of Eggs. 239 
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and after staying in this oviduct a long ora short time, it changes 
its nature there, and then it is laid in places along shores, sandy 
or rocky, in kinds of nest chosen or arranged by the instinctive 
faculties of the mother; after which it is hatched. As to the 
ovula or the egg changing the composition of its liquids during 
its stay in the oviduct:—this ovula while still shut up in its 
ovarian capsule, is more or less opaque, on account of the fat 
which it contains. Detached, it becomes transparent, the yolk 
surrounded by its albuminous matter is clearly visible, unless its 
Vitellin membrane be of appreciable thickness, and the ichthulin 
of which we shall soon speak, is replaced by albumen. Thus 
the egg which shows only some traces of albumen when still at- 
tached to the ovary, becomes very albuminous when it is free in 
the oviduct. In the larger number of fish, the ovary is double. 
We have spoken of the prodigious number of eggs layed by some 
of them, and we could cite numerous examples. The number in- 
creases in proportion to the size of the females and the smallness 
of the eggs. As they are almost all of the same weight and size, 
We weigh the ovary and by counting the number of eggs in a 
gramme, we can estimate pretty closely, the entire number devel- 
. Oped in the ovary. It is in the thick-lipped Grey Mullet (Mugil 
Chelo, Nob.).that we have found as yet the greatest quantity. 
One of this species of the length of 0-60, contained 13,000,000 
*e88; a Codfish (Gadus Morrhua, Lin.) of one metre, gives 
11,000,000; a Turbot (Pleuronectes maximus, Lin.) of 0™-50 
length, lays 9,000,000; we estimated 6,000,000 in a Plaice, 
(Pleuronectes maximus, Lin.) of the length of 0™-30; the carp, 
Whose eggs are the largest, gives only 600,000 or 700,000, when 
from 0™:15 to 0™-50 long. ther fish with only a single ovary, 
have a much smaller number of eggs, than those named. Having 
made an estimate on a dozen large perch of the rivers in Holland, 
Belgium, Picardy, and the neighborhoods of Paris, we found for 
’ mean 71,000 eggs; Bloch gave nearly twfte as many. We dis- 
Covered in the eggs of the osseous fishes immediate principles 
fntirely different from the ichthin of rays and sharks. The 
Study of carps’ eggs enabled us to appreciate these differences. 
arps’ Egos.—On studying under the microscope an ovula 
of a carp slightly advanced, it is seen that the liquid holds sus- 
ed in it a number of little drops of fat slightly colored, in 
the midst of which are to be seen swimming transparent granules, 
tabular in form, which recall those of the vitellus of the ray. The 
— Dorado, vulgarly the Redfish, (the Sea-bream, Cyprinus 
is another species of carp whose ovules present similar 
Small grains mixed with drops of oil. | 
Ichthidine,—In spite of their resemblance in form, the granules 
of which we speak, are not formed of ichthin; for in treating the 
ovula crushed from a carp with a small quantity of water, the 
