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group of Salvelini, or chars, in the genus Salmo. Although one 
parent was the American form, and the other the British, still 
both thrive in our waters. But it is very evident that the 
mortality among the eggs, and the number of deformities 
among the offspring, are far in excess to that which occurs 
when pure American or British forms are interbred,* and as 
this can not be attributed to a mechanical difficulty, some other 
cause has to be found to account for it. As we have no reason 
to suppose that the generative organs of the pure chars (from 
which these hybrids were raised) were in anything but a healthy 
condition, one is led to the belief that some functional change 
must have taken place, which has set up this deleterious 
influence—an influence which diminishes the fecundity of 
hybrids—compared to that observed in pure species. 
The experiment was now varied by crossing the eggs of 
three of the above-mentioned young hybrid char with Lochleven 
trout, when the mortality was 77 per cent. out of 11,800 ova. 
As in the same establishment the percentage of deaths 
among pure breeds is only 4 or 5 per cent., this shows that the 
mortality is enormously increased in hybrid forms; in fact, in 
only one instance, crossing a male smolt or grilse with an adult 
Lochleven trout, was this average of success approached, when 
the loss during incubation was 6 per cent., but the young, in the 
alevin stage, were subjected to an enormous mortality from 
dropsy of the sac. But other things being equal, it seems to me 
that, in the Howietoun experiments, hybrids made among 
fishes nearest related are the most successful—that as hybridity 
as increased the percentage of deaths augments; and were this 
invariably to be the case hybrids would die out. 
Still there seem to be some forms in which this may not be 
the case: possibly the American char and British trout, now 
seen wild in Cardiganshire and elsewhere, is forming a breed 
* One Ichthyologist has subdivided one single species of British trout 
found in fresh waters into six or more, which he terms distinct species. If 
these forms, as Salmo levenensis, is crossed with S. fario, no augmented 
mortality among the eggs, nor monstrosities among the offspring, are seen— 
entirely dissimilar in this respect to hybrids. 
