36 SALMONID^ OF BRITAIN. 



seems to have been the first to point out in America, that although for this 

 purpose the eggs of their common char, Salmo fontinalis, normally require fifty 

 days -when the water is at 50° Fahr., every degree warmer or colder makes five 

 days' difference ; the warmer water acting in expediting the period of hatching, 

 and the colder in protracting it.* But while this is generally correct, it must also 

 be borne in mind that the size and rapidity of the flow, as well as the character 

 of the water, must be taken into consideration. 



Not only will these eggs incubate in damp moss under the conditions 

 described,t but even should they from any cause become dried, such may not 

 necessarily occasion death unless it is continued for some time. On March 13th, 

 1886, at 3 P.M., a trout egg was removed from a hatching-tray where it had been 

 ninety-one days, and the contained young was seen to be very active. It was 

 placed in a dry glass tube, and subsequently forgotten until 7 p.m., when the shell 

 had become dry and somewhat shrivelled, its upper surface having a cup-like 

 depression, which had contracted the size of its interior to about three-quarters 

 of what it had previously been. On examination, the heart of the embryo was 

 seen to be rapidly but feebly pulsating, so it was at once transferred to water, 

 and after little more than half-an-hour the egg had regained its original shape. 

 It hatched seven days afterwards, the little fish emerging in a lively condition. J 



It may be as well to here advert to the result of placing the eggs of the 

 Salmonidae in salt water, for the idea, or conjecture, periodically appears to be 

 revived that salmon can breed in the sea, or at least that it has not been proved 

 that brackish water is deleterious to their eggs.§ It is useless pointing out to the 

 advocates of this opinion, who are mostly prejudiced or ignorant net fishermen, 

 that could they do so, why do salmon push up into rivers for breeding purposes, 

 and that often as far as they can ascend from salt-water influences ? They do not 

 choose a spot between high and low water-mark along our inlets and bays, for 

 in such localities their nests would be liable to be disturbed by the ebb and flow 

 of the tides, whereas if they selected the deeper portions of the ocean possibly 

 the eggs would be insufficiently aerated. 



Rondeletius, who wrote upon the salmon upwards of three and a cjuarter centuries 

 ago, was an upholder of the doctrine that salmon spawned in the sea; one which, 



* Seth Green likewise pointed out, that in the above fishes, when hatched in fifty days, the 

 yelk sac remains thirty more, but if incubation has extended to seventy days, the sac remains at 

 least forty-five. 



■j- The foregoing experiments show that eggs may be kept in damp moss, or other situations 

 destitute of any flow of water, if the conditions of cold, damp and darkness are observed : while 

 the period of hatching may be retarded by the judicious use of ice. It would, consequently, 

 appear practicable to carry on incubation with varying degrees of rapidity, and so suit the time of 

 evolving the young to the capacity of the hatching-house, or even to do without the latter, should 

 the fish-culturist possess proper shallow ponds fed by streams in which to turn the eyed-ova or 

 hatching eggs, a subject which wiL be again alluded to. 



X Dr. John Davy, in 1853, made some interesting observations on the subject of temperature 

 on ova and young fish, in each instance the experiment being carried on in a thin glass vessel of 

 the capacity of about four ounces, nearly full of water, and this vessel was placed in a water bath 

 of the temperature required. An ovum was two and a-half hours in water at 70 deg., which 

 rendered its circulation languid ; kept two hours more, and increasing the heat of the water 

 to 80 deg., no further apparent ill effects were seen. The vessel was now removed from the bath, 

 and allowed to cool gradually, and ten hours later a vigorous young fish was found to have burst 

 its shell. An ovum and a young fish were kept in water between 68 deg. and 72 deg. for about eight 

 hours, when the egg was found to be hatched and a tolerably active young fish was produced. Next 

 day both were exposed to a temperature between 70 deg. and 80 deg., rarely reaching 80 deg., and 

 at the end of the day they were languid, or if in motion disposed to irregular movements. Eemoved 

 from the water bath the next day they were active, and subsequently showed no ill effects from 

 their treatment. A young fish and an ovum were put into water raised to 82 deg., and after an 

 hour to 85 deg., when the water was gradually cooled, but the circulation in the young fish was 

 found to be languid, and the following day it was dead. The egg did not suffer materially for three 

 days ; subsequently a vigorous young fish was produced. An ovum kept in water for two hours 

 at from 90 deg. to 95 deg. died, as did also one put for half-an-hour in water at 100 deg. 



§ In January, 1882, Mr. Douglas Johnstone recorded in a Montrose newspaper that a beautifully 

 marked salmon-smolt, six inches long, had been taken from the stomach of a whiting caught 

 in the deep sea fishing two miles off the Forfarshire coast. Having sent the specimen and 

 necessary information to Professor Huxley, p.b.s., H.M. Inspector of Salmon Fisheries, he was 

 informed by him that this raised the novel and interesting question whether salmon spawn in the 

 sea or not ? 



