207 
meshes of the innumerable drift nets stopped all the larger 
salmon, but let all the small ones through. The eggs when 
taken proved to be at least a third smaller than those of most 
previous years, and the average number of eggs to the fish 
was about 3,500, against 4,200 in the previous year. In this 
instance the smaller salmon produced the smaller eggs, but 
whether the decreased number was not due to the decreased 
size of the spawners is not evident. Livineston Stone 
adduces another instance, asserting that American trout or 
charr living in spring water (which means deficient food) 
develop smaller eggs than such as reside in brooks. Or poverty 
in food has the same effect as younger and smaller fish in 
diminishing the size of ova. This of itself would lead one to 
suspect that small eggs which may be caused by deficient 
sustenance in the parent will not produce the largest fry. 
This difference in the size of fish eggs, which among Salmonidee 
increase in bulk up to a certain age, must have very important 
bearings upon their artificial breeding. For the size of the 
micropyle is in a certain ratio to the size of the eggs, conse- 
_ quently larger eggs of the same species will admit larger 
_ spermatozoa than smaller ones. It has been maintained by 
some fish culturists that very great difficulties, sometimes even 
amounting to impossibilities, occur in crossing salmon with 
trout, or rather fecundating the eggs of trout with the milt of 
the salmon. As this was not found difficult at Howietoun when 
the eggs were taken from fish some years in the ponds, and 
_ which eggs were approaching in size those of the salmon, it 
_ appears to me that the difficulty is merely a mechanical one, due 
_ to the size of the micropyle, a difficulty which has disappeared 
at Sir Jams Gusson Marrnann’s. Here, I believe is a complete 
a solution of how to obtain crosses between the salmon and the 
trout. 
On November 15th, 1882, 2,000 ova were taken at Howietoun 
_ from a Loch Leven trout and fertilised by the milt of an 
_ American charr (Salmo fontinalis) ; one in six did not come to 
‘maturity, dying duringincubation. On the same day 8,000 eggs 
_ were removed from an American charr and milted from a 
