FECUNDATING THE OVA OF THE SALMONID.E, ETC. 83 



lislied in the * Perth Courier,' in April last, and wliich said tliat 

 Dr. Robertson, ' conceiving tliat the ova of the female were im- 

 pregnated, previous to their development, within the body of the 

 fish,' took some ' live female trout from the spawning-bed, and 

 having extracted the roes, deposited them in a perforated zinc box,' 

 which was placed in a running stream in October last, and he 

 found in April (following) that several of the ova had hatched. 

 The author then considered that this alleged experiment of Dr. 

 Robertson could only be solved by one of the following methods : 

 First, that the ova of the female trout had in some way received 

 the influence of the fecundating principle of the male trout previ- 

 ous to Dr. Robertson's depositing them in his perforated zinc box; 

 or, second, that the perforated zinc box, which contained the ova, 

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

 ivithin the fecundating influence of the males ; and of these two 

 solutions Mr. J. Hogg gave detailed explanations." 



The second, and longer abstract, or report, appeared two or 

 three months after the former date, in the " Proceedings of the 

 Linnaean Society," No. 52, p. 246. I add this extract from it: — 

 " 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, ivithin the body of the fish,' had taken ' a number of 

 live female Trout from the spawning-bed, and having extracted 

 the roes, 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 fecun- 

 dating 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 ivitliin the fecundating influence 

 of the males. The former solution he founds on the mode of 



