64 LIFE AND HISTORY OF A SALMON. 



Shaw and Young, and still more recently by those of 

 Dr Davy, as communicated to the Koyal Society of 

 Edinburgh. All these careful observers declare that 

 not the slightest sign of vitality could they ever per- 

 ceive in the ova of salmon or of trout, unless previously 

 impregnated by contact with the milt. As to the inap- 

 titude of the organs of salmon for coition, Dr Davy's 

 anatomical reasoning is conclusive. 



Dr Davy also points out the probable source of Dr 

 Kobertson's mistake, when he fancied that he had suc- 

 ceeded in hatching trout from ova not impregnated by 

 milt. l( The box containing them, was placed in a 

 stream. What is more likely than that they might 

 have been impregnated so included, but not insulated 

 by the spermatic granules, the spermatozoa of milt 

 shed by some fish in the adjoining water ? The diffu- 

 sibility of these living granules not the least remark- 

 able of their qualities seems to be favourable to this 

 conclusion." 



In confirmation of Dr Davy's supposition that the 

 o'va of the trout deposited in the stream were accident- 

 ally impregnated by floating particles of spermatic 

 fluid, we recall the singular experiment of Spallanzani 

 in artificially fecundating the ova of toads. He found 

 that to touch them once with the point of an extremely 

 fine needle was enough to render them prolific. Until, 

 therefore, the ova of trout or salmon are fertilised under 

 circumstances rendering the access of the smallest por- 

 tion of the male sperrn impossible, we cannot attach 

 importance to the theory of Mr Stoddart, or to the un- 

 satisfactory experiments of Dr Eobertson. 



The ova, then, of the salmon being deposited after 

 impregnation in the manner described, we have now to 

 trace the process of their vivification. Of this we are 

 not aware that we have any detailed and perfectly 

 trustworthy account until the publication, in 1843, of 

 * Observations on the Natural History of the Salmon/ by 

 Robert Knox, F.K.S.E. While cheerfully acknowledg- 



