70 



Plenty for several days, during which they exhibited the 

 migratory instinct very strongly, and several died. After 

 carefully examining the survivors, my fellow-commissioner 

 (Mr. Eobert Read) and myself, let the school follow their own 

 instiucts, and proceed down the Biver Plenty. Three of the 

 specimens which died are now in the Museum, and two of 

 these I have carefully dissected. Before giving the results of 

 these dissections, I desire to remind the Fellows of the Society 

 that within a week of this same date last year a school of fish 

 were observed iu a millrace running from the Bagdad rivulet, 

 that one of those fish (now in the Museum) was sent to me 

 for determination, and that I then expressed my belief that it 

 was an immature specimen of the large silvery variety of the 

 brown trout (Salmo fario) which are now numerous in the 

 brackish water of the Upper Derwent. Mr. John Buckland, 

 who assisted me in the examination, concurred in this view 

 as to the species of the Bagdad fish. 



Upon placing the Bagdad and Plenty fish side by side, it will 

 be evident to the most casual observer that they are identical 

 in species, and the dissections confirm me in my belief that 

 both schools are the progeny of the silvery variety of Salmo 

 fario. One marked peculiarity of the smolts of the true 

 salmon (Salmo salar), and of the salmon trout (Salmo trutta), 

 is the deciduousness of the silvery scales, for some time after 

 they are first assumed the slightest touch removes them, and 

 when the fish are handled the fingers get silvered over with 

 the brilliant scales, but the Bagdad and Plenty fish bore con- 

 siderable rubbing without losing their bright covering. Again, 

 the smolts of the true sea-going species, even for some time 

 after they reach the sea, show the original parr markings 

 distinctly whenever the scales are removed, but on removing 

 the scales of one of these fish no trace of parr markings could 

 be found. In one of the tests given by Dr. Giinther, as most 

 constant, namely, the number of scales between the last dorsal 

 fin, and the lateral line, the Bagdad and Plenty fish all failed, 

 the numbers in every instance being those of the brown 

 trout, while the smolts from the lower Derwent have always 

 exhibited the number typical of the true salmon. In one of 

 the Plenty specimens the spawn was found more developed 

 than it is usually seen in the smolt of the true salmon before 

 it has reached the sea. 



The result, of counting the pyloric coeca has been to shake 

 my belief in the value of that test for specific distinction. In 

 the Bagdad fish the number was rather more than the average 

 given by Dr. Giinther for the brown trout (Salmo fario) . In 

 one of the Plenty fish the number was more than the maxi- 

 mum for brown trout, and above the average for salmon 



