472 Linncean Society. 



through which the stream was continuously flowing, had nearly all 

 produced young salmon by about the middle of April. Some expe- 

 riments made about the same time by the late Earl of Tyrconnell 

 failed of success from want of attention to the locale. Attempts 

 •were also made by Henry Coxe, Esq., of Scruton Hall, and Major 

 Wade of Hanxwell Hall, to breed artificially from Trout, in which 

 the latter gentleman had succeeded. After pressing the subject on 

 the attention of all who may have the opportunity of making expe- 

 riments, Mr. Fisher concludes his letter by a caution against what 

 he considers an incorrect statement, taken from the Perth Courier, 

 in which it is said that Dr. Robertson of Dunkeld, " conceiving 

 that the ova of the female were impregnated previous to their 

 development, within the body of the fish," had taken " a number 

 of live female trout from the spawning-bed, and having extracted 

 the roe, deposited them in a perforated zinc box, containing also 

 some gravel," which was " upon the 14th of October last placed in 

 a running stream, and on examining the box [in April], several of 

 the ova were found to be hatched." On this latter experiment Mr. 

 Hogg observed, that the result could only be accounted for by one 

 of the two following methods. Either the ova of the female trout 

 had in some way received the influence of the fecundating principle 

 of the male trout, previous to Dr. Robertson's depositing them in his 

 perforated zinc box ; or, the perforated zinc box, which contained 

 the ova as expressed from the females, was placed in the running 

 stream within the fecundating influence of the males. The former 

 solution he founds on the mode of spawning described by Mr. Ellis 

 in his ' Natural History of the Salmon,' from which it would appear 

 that the male and female fishes having jointly made a furrow in the 

 gravel, place themselves one on each side of it, and throwing them- 

 selves on their sides " again come together, and rubbing against 

 each other, both shed their spawn into the furrow at the same time. 

 This process is not completed at once ; it requires from eight to 

 twelve days for them to lay all their spawn." Mr. Hogg argues 

 from this description, that it is possible that the female trout from 

 which Dr. Robertson took the ova might have gone through this 

 process with the male, and might have thus received the fecundating 

 influence, just before she was caught ; but on this solution he does 

 not rely. He thinks it more probable that in the running stream in 

 which the perforated zinc box was placed, there were some male 

 trouts which had deposited their milt near the box, and that some 

 of the milt might have been carried with the stream through the 

 holes of the box, and have so fecundated the ova within it. In con- 

 clusion, he suggested, that as doubts still exist as to the processes 

 which the male and female salmon and trouts naturally adopt at the 

 spaw^ning season, experiments on the subject might readily be un- 

 dertaken, by confining them, at the proper seasons, in large glass 

 cases or tanks, covered over with a coarse wire gauze, such as those 

 which have recently been constructed in the Water-vivary of the 

 Zoological Gardens, as a name for which he suggests the word 

 Hi/drozogrium, compounded of v^up, aqua, and l^ioypelov, vivarium. 



