
DR DAVY’S OBSERVATIONS ON THE CHARR. 323 
roughly dried, so as to expel this moisture, they were reduced from ‘10 to ‘07 of 
a grain, thereby denoting a large proportion of solid matter, viz., 70 per cent. 
Whether this shell in its sound state, before putrefaction has commenced, is 
pervious to water, seems to me questionable; and also, whether the internal 
vitelline membrane, after fecundation, is altogether impermeable by it. M. Voer 
holds that the shell is at all times so permeable, but the vitelline membrane, 
after impregnation, never, so long as the ovum retains its vitality ; losing which, 
the membrane, he infers, no longer resists the transmission of water, and the 
coagulation of the fluid yolk takes place as an unavoidable consequence. I might 
assign reasons for the doubts I venture to entertain on these points; but not sure 
that they would be considered satisfactory, or that the points themselves, though 
not without interest, require here to be discussed, I shall avoid bringing them 
forward. That the death of the impregnated ovum, as pointed out by M. Voar, is 
clearly indicated by the coagulation of the yolk, from the penetration of water into 
its substance, is certain. But there is another indication of the event, and not less 
certain, viz., the adherence of the lighter oil globules to the vitelline membrane, 
preventing thereby their change of place with a change of position of the ovum, 
and that tendency to ascend in the heavier yolk fluid which is observable whilst 
vitality lasts, and which may perhaps be considered as a characteristic of it. The 
adhesion of the oil globules alluded to, not unfrequently takes place in eggs which 
retain their transparency. In no instance have I observed any traces of foetal 
development after these have become fixed, or, if commenced, any further pro- 
eress. Why these ova do not become opaque, why their membranes should re- 
main impervious to water, I am ignorant; but that they are so, must be inferred 
from the circumstance, that when ruptured, and their contents mixed with water, 
coagulation is immediately effected. 
Relative to the milt or spermatic fluid of the charr, I have but few observa- 
tions to offer, the examination I have hitherto made of it not having been minute, 
except very partially. Like that of the Salmonidee generally, in its mature state 
when ready to be shed, it is a milk-like fluid, slightly viscid, heavier than water, 
and containing, diffused through it (the cause of its milkiness) a vast number of 
granules (spermatozoa). These minute bodies are nearly spherical in form, are 
about ;mnth of an inch in diameter, and seem to move spontaneously, as seen 
under the microscope, for a short time after the expulsion of the fluid from the 
live fish. Though they are of greater specific gravity than water, yet, owing to 
their minuteness, they are easily diffused and suspended in this fluid. After a 
rest of two hours, water rendered turbid by the addition of a small quantity of 
spermatic fluid had not become clear, even towards its surface. A drop placed 
under the microscope was found to abound in spermatozoa. Another property of 
the spermatic fluid, not unworthy of mention, is the remarkable manner in which 
it resists putrefaction. Whether the spermatozoa are capable or not of impreg- 
