270 



SALMONID^ OF BRITAIN. 



(see pp 158, 227 ante) tlie following are some of the observations made at 

 Howietoun : — 



Average length. 



Most 

 bands. 



Least 

 bands. 



10 



Greatest 



difference in 



a single fish. 



2 



2 



2 



3 



7 hybrids of Salmon and Lochleven 11| inches 12 

 4 „ Zebra breed . . 9^ ., 11 



3 ,, Leopard breed . , 9^ „ 11 



6 ,, Struan breed . • 9i ,, 13 



This would appear to show that the difference in the numbers of these par 

 bands in these fishes may be comparatively considerable. 



The number of rows of scales I have found existing in the various chars have 

 been as follows : — 



from adipose dorsal to 1.1. 



18-28 

 21-26 

 20-28 



British char. Scales along lateral-line 125-145 

 American char. „ ,, 122-142 



Hybrid char. „ „ 124-136 



The mode of dentition on the vomer alters in hybrids, as will be seen in 

 fig. 52, showing how the teeth in the char, Salmo fontinalis, are restricted to an 

 angular band of about six or eight situated a,long the hind edge of the head of that 

 bone. But in crossing with trout the number of teeth on the head of the bone 

 decreases, while the knob at the inferior end of the head lengthens along the 

 central line of the vomer, where teeth in trout are situated, and this elongation 

 serves as a dental ridge showing three or even four teeth along it. 



It may be a question whether any prepotency of sex among the parents of 

 hybrids can be detected in the offspring, exhibited either in sexual development 

 or in external characters ? 



Of course as trout and char may equally commence breeding when just under 

 two years of age we cannot expect to find any prepotency of parental sex to be 

 thus shown among the offspring, but it is different wath the salmon, among which 

 we may anticipate spawning at a year later than in the trout. 



In the cross made December 24th, 1881, between salmon and Lochleven 

 trout, and which hatched in March, 1882, the fish were suffocated in July, 1885, 

 but some would evidently have bred that winter or in their third or fourth season 

 similarly to salmon: two which survived, and were males, were employed for 

 breeding, November and December, 1886. 



November 29th, 1883, a salmon joar was employed to fertilize milt of a 

 Lochleven trout, and among the few survivors of the dropsical offspring one 

 female gave eggs November 23rd, ]886, or at 33 months. Consequently in all 

 those instances where the male parent was the salmon the young did not breed 

 before the 33rd month, or similarly to salmon bred at Howietoun, but twelve months 

 later than trout or char. 



No. 52. Teeth on vomer of American char : 1, front view ; 

 Iff, side view : of hybrid between American char and Lochleven 

 trout: 2, front view; 2((, side view. 



Craig-end burn only from 12 to 14, and those much broken up, the food being the same in both 

 localities. The young of sea trout Salmo trutta (sec note in p. 146 ante), on July 6th, 1887, in 

 pond 3 at Howietoun, were found to have 9 complete and some incomplete par bands, while some 

 young of S. fario in the next pond, no. 4, and of similar age, had from 10 to 12 of these bands. 



