252 SALMONID^ OP BRITAIN. 



Seth Green's rule is that these eggs hatch in fifty days, every degree warmer 

 or colder making a difference of five days. 



Hybrids. — These have been made among these fishes as observed (at p. 49 

 ante), and will be further referred to in detail. 



Life history. — Although when a few months old they do not require such a 

 depth of water as trout, and do well kept indoors in rearing-boxes, it is not so as 

 they get older, when, should the ponds in which they are be too small, they seem 

 to stunt the subsequent growth of the fish. But, although it is evident to every 

 fish-cnlturist, that among the same batch of young fish of every species of this 

 family, some grow more rapidly than others, even when kept under identical 

 conditions, the cause of this is not so apparent. Soon after these fish have 

 absorbed the yolk-sac, it is common to observe how the larger ones take the best 

 spots and strongest current of water, while the smaller ones congregate nearer 

 the lower end of the trough where they will be least interfered with, the conse- 

 quence being that the largest fry live where the most food is to be obtained, 

 thus giving them another advantage over their smaller and weaker brethren. 

 Also, fish of different sizes keep together. Over-crowding certainly does much 

 damage (see pp. 43-46 ante). Other things being equal, such fish as have the 

 largest supply of water grow the fastest, while they do better in moderately 

 warm than in cold water, and they should be well fed. In ponds, unless the 

 food is properly distributed, some may be insufficiently fed, when, becoming 

 weak, they do not collect at feeding time. Means have to be taken to obviate 

 this (see History of Howietoun, p. 72). 



Mr. Andrews at Guildford, states that he found that his yearlings ran from 

 8 oz. to 10 oz. and two-year-olds from 1| to 2 lb. each ; three-year-olds averaged 

 4 lb., and four-year-olds go 5| lb. to 6| lb. {Land and Water, July 22, 1882.) 

 Livingston-Stone, Domesticated Trout, p. 253, i'emarked " I have seen a trout 

 that was reasonably believed to be but two years old that weighed a pound, and 

 I have seen one of the same age that barely turned the scales at half-an-ounce." 

 " If you want to dwarf trout, keep them in cold sunless water, in close confine- 

 ment, and with little food, and you will do it." 



Diseases. — Seem to be very amenable to Saprolegnia ferax, and it is very 

 common to see the opercles shortened, apparently owing to having had gill-fever 

 when young. At Howietoun many are believed to suffer from enteritis should 

 the temperature suddenly fall. 



In American streams they are said to generally disappear when the trees are 

 cut down, probably because their constitutions are unsuited to waters subject to 

 rapid changes of the temperature, although they are able to stand a considerable 

 heat at times. 



As food are excellent, the flesh may be white, perfectly pink, or of a deep 

 red.* 



* Mic-Mao, ■writing from Boston to The Field of April 22nd, 1882, observed, "By-the-bye, I see 

 that Mr. Francis Francis speaks well of our trout, i.e., Sahno fontinalis, as a table fish. If he 

 found the ones he had, which he says were white-meated, good, I only wish I could send him a 

 brace of good Cape ' salters.' We do not consider a white-meated trout as fit to eat, although I 

 have eaten some, when taken out of a cool pool with rooky bottom and white sand margins, that 

 were white in colour and with white flesh, but yet sweet and palatable. But I think there can be 

 no doubt that to get them in their perfection the flesh should be red, or at least pink. We have 

 a theory that feeding on shrimps has a great deal to do with the colour of the flesh ; it most 



