Composition of Eggs. 45 
labor, showed us that the yellow of the eggs of sharks, still in 
the ovarian capsules, offers the same composition as those of 
Ray’s eggs. Our observations are then established wholly by 
comparison. 
Eggs of the Angel-fish, (Squatina angelus, Dum.)—We were 
not able to obtain more than one female this year, and all its 
ovules were still in the ovarian capsules, under the stroma of the 
ovary, which, in form, texture and even color, is more like those 
of the Ray than the sharks. We carefully gathered the yolks 
about to develop; we found in them, as in the former, a fatt 
matter divided into drops, swimming in a viscous albuminous li- 
quid, with a great number of grains of peculiar form. 
3. Of Ichthin. 
Our observations on the eggs of so varied species and kinds of 
Cartilagine, bring us to the immediate analysis of the different 
yolks, After ascertaining that the grains suspended in the liquid 
were insoluble in water, and that this liquid did not thicken with 
water, the next step became very simple. 
After taking proper precautions for running the yolk without 
mixing, into a large quantity of distilled water, the grains, which 
were denser than the water, fell to the bottom, and were washed 
by decantation, till the washing-water had no more trace of al- 
bumen or of salty matters. The grains were entirely freed from 
the fatty matter by successive washings in alcohol and ether. 
There remained after this treatment, a large quantity of grains, 
from which it is easy to get in some hours, several hundreds of 
grammes, which present under the microscope, every character- 
istic of absolute purity. 
The analysis which we will now briefly describe, then showed 
us that the vitellus of an egg of the Cartilagine is formed of a 
albuminous liquid, holding in solution some mineral salts, princi- 
pally chlorids and phosphates, and suspended white grains of an 
€ven and regular form in each species but varying in one species 
from another, and mixed with a small quantity of phosphuretted 
. fat. This fatty matter is soluble in alcohol and ether ; it forms with 
water a sort of mucilage; it shows some analogy to the fat-acid 
which is found in the stag, described by one of us as oleophos- 
Phoric acid. As for the white grains, they seem to us to consti- 
tute quite a new principle, whose properties and composition we 
Shall describe as ichthin. Ichthin is pleasant to the touch, and 
presents to a certain extent, the aspect of starch. We obtained 
it by our process, pure, under the form of granules from different 
Species of Cartilagine. : | 
From the Thornback or Clavated Ray (Raia clavata, Lin.), the 
rains of ichthin obtained from the yolk of a freshly laid egg, 
appear in the form of little rectangular tables, with round edges 
