1884.] 



HYBRIDS AMONG THE SALMONID^. 



591 



tuting species so much unnecessary discussion has arisen, and state 

 tliat Mr. Arthur lately observed on the examination of 21 females 

 and 7 males, that the females possessed from 33 to 61, with a mean 

 of 47'3, and the males from 37 to 55, with a mean of 48'7. These 

 two specimens each had 52. This is in fact a further corrol)oration, 

 were any needed, that these appendages are not constant in number 

 but variable. 



In the female there were not so many young teeth coming 

 forward as were seen in the male, while, if the figures of the two 

 heads are compared, it will be seen that the length of the head in 

 the male is elongated beyond what is perceived in the female, solely 

 in the space anterior to the nostrils. 



Fig. 3. 



Head of Lochleven Trout. 



This brings me to a short consideration of the hook on the lower 

 jaw of male Trout ; and as it has been so confidently stated by 

 Dr. Giinther of the Lochleven Trout, " Snout of moderate length, 

 conical, not much produced in the male sex, in which a mandibular 

 hook has never been observed" (Catal. Fish. vi. p. 101), I produce 

 an example demonstrating this hook (see fig. 3), differing, it will be 

 seen, from what occurs in the large Otago specimen, in that the hook 

 is here in front of the upper jaw when the mouth is closed. Tlie 

 specimen was reared at Howietoun from eggs taken at Lochleven in 

 1878, and it had 69 caecal appendages. 



