252 DR DAVY ON THE SALMONIDZ. 
places of the charr. In this instance the young fish, after the disappearance of 
the yolk, throve well, and, as I believe, chiefly on the infusoria present. This in- 
ference was made partly in consequence of finding, on microscopic examination, in- 
fusoria on the plants and stones and sides of the vessel, and vestiges of them in the 
excrements of the young fish, and in the intestine of some that were opened, and 
partly from observing how the young fish, when in pursuit, as it was supposed, 
of food, seemed to confine themselves to the spots where the infusoria were in 
greatest numbers. Another reason (were we to reason @ priori on the subject) 
might be assigned, viz., the presumed fitness of these microscopic animalcules for 
the food of creatures of so small a size as the young of the Salmonidee in their 
early stage, and the fitness of the latter, with their microscopic eyes, to see and 
make the infusoria their prey. 
The fish, the subjects of these trials, were all young charr. Those from the 
eggs impregnated on the 25th of November were so advanced by the second week 
in April, as to be considered fit to be set at liberty. Some were taken to a lake 
in the Highlands of Perthshire ; others to a mountain tarn in this neighbourhood. 
Both sets were from the earthenware pan, to which no food had been given. 
I may offer as a suggestion, that where minnows abound, their young, it is 
probable, may be employed as a useful aid for the support of the young of the Sal- 
monide. The time of breeding observed by the minnow, early in May, seems 
suitable, and especially so the minuteness of the ova of this little fish, and of their 
fry when hatched. Their eggs at maturity | have found to be ‘06 of an inch in dia- 
meter; the foetal fish on quitting the egg was about -20 of an inch in length, and 
no more than -35 inch when of its perfect form, as denoted by the growth of its 
permanent fins, which it acquired in a few days. In this stage its weight (moist) 
did not exceed ‘03 grain, and when dried was reduced to -01 grain ! * 
7. Of the Parr. 
As discussion, wherever doubt exists, is always useful, so that it be tempe- 
rately conducted, and lead to further inquiry, I venture to bring under the notice 
of the Society the question, the vexed question, whether there be or not a fish of 
the family of the Salmonidze, a parr having so close a resemblance to the salmon 
fry as to be with difficulty distinguished, and yet a distinct species. 
* The above results were obtained in the month specified. The eggs were from minnows from 
the river Rothay, a tributary of Windermere. On the 6th of May, they were impregnated by the 
artificial process, and placed in water, varying in temperature from 50° to 54°, which was changed 
daily. One fetal fish burst its shell on the 11th of May; the next on the night of the 12th; the 
majority on the following day ; some did not appear till the 15th. On the 31st of the same month, 
most of them had acquired their permanent fins. 
In substance, the eggs of the minnow were found similar to those of the Salmonide, being com- 
posed of oil globules, and of an albuminous fluid, coagulable by admixture with water. 
Some of the ova to which no milt was added—the omission intentional—died without showing 
the slightest appearance of organic development. 
