506 Transactions. — Miscellaneous. 



This table means that among females the least variation is among the 

 dorsal fins, which variation goes on increasing to a maximum in the anal 

 fins. Among males the variation is nearly the same among all the fins 

 but the ventral, and not at all to be compared in amount with that of the 

 females as before stated. 



In the fin rays, nothing in the way of change has been seen by me 

 during the past five years, so that I can but repeat that I find the dorsal 

 and pectoral fin rays vary by one or two in number ; the ventral and the 

 caudal appear to be constant, while the anal differs by one ray at times. 

 Thus 12-14 D ; 13-14 P ; 9 V ; 10-11 A; and 19 C, will be the fin ray 

 formula ; and I may explain the numbers in the dorsal and anal fins 

 include simple spines, but those of the caudal do not, there being usually 

 four to six spines additional on either side supporting the base of the fin. 

 The caudal seems absolutely invariable as to number of bony and feathered 

 rays, 19 being constantly found by me. Then the ventral is almost as 

 constant, as I have never seen more than one or two cases where the rays 

 differed from 9, and then only by one ray. The dorsal and pectorals may 

 be taken as invariable within the limits of one to four rays ; and, in short, 

 within these limits all the fin rays appear to be fixed in number. It is also 

 to be remarked that a comparison of the fin ray formula above with those 

 given by Yarrell, Giinther, and others, shows no practical difference. 

 Neither is the difference greater when compared with the formula of the 

 8. salar and S. trutta, so that the number of fin rays is really of no specific 

 value as a distinction among these closely-allied species. 



Scales. — The most constant in number are those in a row from adipose 

 fin back, or forwards to lateral line — probably, however, apparently so 

 only, because they are more easily counted — those taken along whole 

 length and breadth of body being very hard to see at head and tail, and 

 along back and belly. Twenty-three female trout and nine males I found 

 to have 14 to 18 scales from the adipose back to lateral line. Lat. L. 117 

 to 128, and Trans. L. 48 to 66. The trout having these scales were from 

 14ozs. to lllbs., taken from fourteen different rivers or waters. Neither 

 sex nor age showed any real difference in the numbers. 



The Vertebrte of our trout, so far as I can make them out, are fixed in 

 number ; that is, they only vary from 56 to 60. As, however, I have found 

 great difficulty in deciphering the terminal bones at the head and tail, I 

 cannot claim greater accuracy than to within one or two. Out of sixteen 

 trout examined, one had 56 vertebrae, three 57, two 58, seven 59, and three 

 60. There does not appear to be any correlation between the sexes and 

 the number of vertebrae ; thus the mean number among eleven females was 

 58*5, and among five males, which are all I have a record of, was 58"4. 



