12 



SOME FURTHER NOTES ON THE INTRODUCTION 

 OF THE SALMON INTO TASMANIAN WATERS. 



By M. Allport, F.L.S., F.Z.S., &c, &c. 



[Read 10*A March, 1874.] 



On the 4th of December last there was captured in a tide- 

 pool at Bridgewater, a fish which the Salmon Commissioners 

 have decided to be a true salmon (Salmo salar) in the grilse 

 stage, that is on its first return from sea, and acting on such 

 decision the Government have paid to the captor, Mr. Joseph 

 Cronley, the promised reward of =£30. 



As was to be expected, some of those who have persistently 

 expressed doubts as to the possibility of ultimate success have 

 made attempts to call in question the species of this fish, but 

 have failed to point out any feature in which it differs from a 

 true Salmo salar in its grilse stage. 



It is often extremely difficult, even for a naturalist, to 

 distinguish between nearly allied species of any given genus 

 of animals, because the points of resemblance are numerous 

 and striking, and immediately force themselves on the 

 observer, while the points of dissimilarity are few, and often 

 so obscure that they have to be laboriously sought out. To 

 clear away some of this difficulty before attempting to explain 

 the reasons on which the decision of the Commissioners was 

 based, I must briefly refer to Dr. Giinther's introduction to 

 the Salmonidse in the sixth volume of his most valuable 

 Catalogue of Fishes in the British Museum. 



The learned Doctor divides the characters by which the species 

 are separated from one another into two sets, namely, those 

 which vary with age, difference of food, locality, &c, and there- 

 fore are of small value for specific distinction, and those which 

 are found to be constant in numbers of individuals, and in 

 which it is difficult to perceive signs of modification due to 

 external circumstances. 



The variable characters are :— First, colour ; second, size ; 

 third, proportions of various parts of the body to one another ; 

 and fourth, differences in the fins, such as number of rays, &c. 



The constant characters are :— First, form of the prceoper- 

 culum in the adult fish ; second, width and strength of the 

 maxillary of the adult fish ; third, size of teeth ; fourth, 

 arrangement and permanence or deciduousness of the vomerine 

 teeth ; fifth, the form of the caudal fin in specimens of a given 

 size, age, and sexual development ; sixth, the size of the 

 scales as indicated by the number of transverse rows above the 

 lateral line — one of the most constant characters ; seventh, 

 the number of vertebrae ; and eighth, the number of pyloric 

 appendages. 



