Flow to obtain tt. 251 
but they are to be carefully kept out of the stock ponds, which 
are afterwards destined to produce fish in abundance for many 
waters. 
In a state of nature trout often develop considerable de- 
formities, and here we have the advantage, by careful selection, of 
avoiding much of the risk of producing monstrosities and malfor- 
mations, such as are found naturally in many localities. Cases 
have been recorded of blind trout occurring extensively in some 
natural waters, as for instance in the Fischau, near Mandorf, in 
Germany. I have met with cases myself, both of total and partial 
blindness, and instances have been recorded in which trout were 
found to be blind in one eye only. ‘Probably the last-mentioned 
cases have been due to external causes, but I am satisfied that 
instances of blindness occur amongst trout which are the result of 
disease or hereditary weakness of some kind. Blindness is well 
known to scientists to occur amongst other fish also. 
Deformities of the jaw and head are not uncommon in some 
lakes, and, from experiments which IJ have carried out, I am 
satisfied that inter-breeding is one of the causes. Sometimes the 
upper jaw is arrested in its growth, and becomes much shorter 
than the lower one, whilst sometimes the lower one is similarly 
affected. In some cases the lower jaw becomes so fixed that the fish 
cannot close its mouth, and occasionally instances may be met 
with in which the opercles or gill covers, instead of lying close, as 
they should do, stand out at a considerable angle, and when fish 
so affected are looked at straight in the face, their faces have the 
appearance of being surrounded by a sort of Elizabethan frill. 
In the island of Islay is to be found a race of tailless trout, and the 
hunchbacked trout of Plinlimmon, in Wales, have been alluded 
to by many writers. These and some other deformities may be 
caused’ by the fish being carried over waterfalls, as has been 
suggested, but, on the other hand, there are many streams of the 
same kind in which such cases do not occur. It is beyond 
dispute that-a fall from a height is liable to injure the spine of a 
fish, and some crooked spines may be produced in this way. 
This, however, would not account for the deformities of heads of 
fish, and for the deficient gill-covers which have been found to exist. 
“Remarkable malformations are observed in the trout of 
