322 DR DAVY’S OBSERVATIONS ON THE CHARR. 
pressure applied to the abdomen, soon after the fish were taken from the water,— 
the roe in detached ova, the milt in the state of a milk-like fluid. 
It was from these boxes that I obtained, through the kindness of their pro- 
prietor, most of the subjects of the following observations; and to him, too, I was 
indebted for exact particulars, without which the observations would have been 
almost valueless. 
1. Of the Roe and Milt of the Charr. 
The ova of the charr, at their full time, that is, when they are detached from 
their ovaries, and are loose in the cavity of the abdomen, ready for expulsion, are, 
like those of the other Salmonidee, almost, if not quite, spherical. Those I have 
examined, I have found to vary in diameter from ‘16 to °18 and :20 of an inch; 
and in weight (after the removal of adhering moisture by wiping) from °7 grain 
to 1 grain each. Their colour is a light yellow, lighter than that of the ova of 
the salmon or lake trout with which I have compared them, and thus distinguish- 
able, as well as by their somewhat smaller size. The matter of which they con- 
sist may be described as an almost colourless, transparent, viscid fluid, contain- 
ing suspended in it very many oil globules of various sizes, hardly distinguishable 
without the aid of the microscope, of a yellow colour, to which the colour of the 
egg is principally owing. This matter may be considered as corresponding to 
the yolk of the egg of the bird: it is more than doubtful that the ova of the 
charr have any part corresponding to the albumen of the bird’s egg. The matter 
of the charr’s egg, I may remark, like that of the ova of the Salmonide generally, 
is peculiar in some of its properties; being coagulable on admixture with water, 
as I believe was first pointed out by M. Voar, in the instance of the Coregonus of 
the Lake of Neuchatel,*—in being, as I have found, not coagulable by heat, even 
at a temperature of 212° Fahr., if water be excluded,—in being, after coagulation 
by water, soluble in a solution of common salt and in other saline solutions, and 
also in such of the vegetable acids as were tried, for instance, the tartaric, acetic, 
oxalic, and citric. For a fuller account of these experiments, I may refer to a 
paper expressly on this subject, which has been communicated to the Royal So- 
ciety of London, the results of which would seem to Show that the substance of 
the egg of the Salmonidz may be viewed as a distinct species of albumen,—as 
much so, perhaps, as the coagulable lymph of the blood compared with the serum 
of that fluid. 
The shell of the egg of the charr may be briefly noticed. Nearly transparent 
and colourless, it is of considerable strength, and until thinned and weakened in 
the process of hatching, is not easily ruptured. Five emptied of their contents, 
but not deprived of their moisture by drying, weighed one-tenth of a grain; tho- 
* See ‘ Embryologie des Salmones. Par C. Voer.” Neuchatel, 1842, 4to, p. 11. 

