224 ANNALS OF SCOTTISH NATURAL HISTORY 



On the other hand there are malformations whose 

 origin we cannot trace. They seem to develop so naturally 

 that they are said to have been preordained from the very 

 egg. Such are " congenital variations," and to this group 

 the case which forms the subject of the present notice 

 appears to me to belong. 



The specimen was caught in the neighbourhood of 

 Stranraer, Wigtownshire, in July 1908, and was presented 

 to the Royal Scottish Museum by Dr. C. McNeill. It is a 

 common trout {Salnio fario^ Linn.), small in size, and differ- 

 ing from a normal specimen in possessing a short thick-set 

 body, with a depth much greater than fair proportion would 

 allow. To this disproportionate depth and to a consequent 

 bulging of the contour behind the head is due the hump- 

 backed, perch-like appearance of the specimen. The following 

 measurements give some idea of the more important dimen- 

 sions : — total length (tip of snout to centre of tail), 120 mm. ; 

 length of body (tip of snout to base of tail), 1 1 2 mm. ; 

 length of head, 3 5 mm. ; breadth of body in front of dorsal and 

 ventral fins, 46 mm. ; distance between base of adipose fin and 

 base of tail, 9 mm. But a better notion of the significance 

 of those numbers will be obtained by comparing the propor- 

 tions with those of average specimens. Thus, while Day ^ 

 gives the total length of the body as from 4^ to 4|- times 

 that of the head, in our specimen the numerical relation is 

 only 3|-. And whereas, according to the same author, the 

 length of body ought to vary between 4|- to 5 times the 

 breadth, our proportion is 2^. A glance at the specimen 

 shows further that the head and fins are in fair proportion, 

 and that they are of a size suited to a longer individual. 

 It would appear, then, that the disproportions are due to an 

 actual shortening of the body. 



This conclusion was confirmed on dissection, for, the 

 vertebral column having been exposed, it became clear that 

 in it lay the apparent cause of malformation. Instead of 

 the usual number of from 56 to 60 vertebrae only 40 could 

 be distinguished. And yet the full complement of neural 

 spines was present, and agreeing with them were equivalent 



1 F. Day, "Fishes of Great Britain and Ireland," vol. ii. p. loi. London, 

 1880-1884. 



