FECUNDATING THE OVA OF THE SALMONID^, ETC. 81 



the influence of tlie fecundating principle of the male Trout, pre- 

 vious to Dr. Robertson's depositing them in the perforated zinc 

 box ; or, second^ that the ' perforated zinc box,' which contained 

 the ova or roe, as expressed from the females, was placed in the 

 * running stream,' ivitlwi the fecundating influence of the male 

 trout. 



" In explanation of mjflrst solution, I will cite the following 

 passage from Mr. Ellis's * Memoir on the Natural History of the 

 Salmon,' wherein he describes the mode of spawning. ' A pair of 

 fish are seen to make a furrow, by working up the gravel with 

 their noses, rather against the stream, as a salmon cannot work 

 with his head down stream ; for the water, then going into his 

 gills the wrong way, drowns him. Wlien the furrow is made, 

 the male and female retire to a little distance, one to the one side, 

 and the other to the other side of the furrow ; they then throw 

 themselves 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 8 to 12 days for them to lay all their spawn, and when 

 they have done they betake themselves to the pools to recruit 

 themselves.' 



" If Trout follow the method here stated by Ellis as that 

 which Salmon do sometimes adopt — ^namely, of ' coming together 

 and rubbing against each other' — it is possible that the female 

 trout from w^hich Dr. Robertson took the ova, might have per- 

 formed this process with the male, just before she was caught, 

 and by that process those ova, which were then ready for being 

 deposited, might have received the fecundating influence of some 

 of the milt (the spermatozoa) from the male. But whilst I men- 

 tion the mere possibility of this solution, I do not rely upon it. 



" Again, as to my second, and more likely solution : In Dr. 

 Robertson's experiment, as published in the ' Perth Courier,' it 

 is not stated that the Doctor placed the zinc box, containing the 

 ova and some gravel, in a running stream, where no male trouts 

 were to be found. Consequently, it is exceedingly probable that 

 in the same running stream there were some male trouts, which 

 had deposited their milt near the zinc box, which is expressly 



