ON MALFORMED TROUT FROM SCOTTISH WATERS 97 



amount of dichotomisation : besides which they show also a 

 tendency to coalesce at their terminations, then by the convergence 

 downwards of the upper long rays, and upwards of the lower 

 ones, the fin comes to present a rounded instead of the usual 

 broad fanshaped form. I have examined one species in which all the 

 fins but the caudal are normal as regards the development of the 

 rays, but in others, as in the specimen described above, the pectoral 

 and anal fins are also more or less affected in the same way. 

 Nevertheless in no case have I seen any such affection of the rays 

 in either the dorsal or the ventral fins, though the latter indeed 

 sometimes appear smaller than usual. 



ii. Trout from Loch Enoch. 



The three specimens from this lake which I have examined 

 resemble each other very closely in general appearance. They are 

 small, measuring respectively 5§ , 6, 6 J inches ; they are dark-coloured 

 and closely spotted ; the head is rather large in proportion to the 

 body. In Plate V, Fig. 1, is represented one of the original speci- 

 mens given to the Museum by Air. Harvie-Brown in 1881. Here the 

 caudal fin presents an abnormal condition of exactly the same nature 

 as in the Loch-na-Maorachan specimens, — only the stunting of the 

 development of the fin seems to be carried to a still greater extent. 

 Of the other fins the anal is distinctly stunted in development and 

 abnormal in its shape, being low and rounded instead of triangular- 

 acuminate ; the pectorals and ventral are rather small, the dorsal is 

 normal. 



In one specimen, not figured, the malformed caudal has assumed 

 a slightly oblique unsymmetrical contour, while the anal has become 

 most remarkably stunted in its development. None of the other 

 fins save the dorsal are normal in their development, and the princi- 

 pal rays of the right pectoral are coarse, stiff, and slightly contorted. 



iii. Trout from the River Carron. 



Two specimens of Trout with malformed tail fins from the River 

 Carron near Larbert have been given by Mr. Harvie-Brown to the 

 Museum of Science and Art, and are now before me. 



The first (Plate IV. Fig. 1) measures 1 1 inches in length, and 

 resembles an ordinary river trout in everything save the condition 

 of the caudal fin, and to a small extent also of the anal. The tail 

 fin is not broadly expanded, nor can it be expanded by pulling it 

 with the fingers; its upper and lower mar-ins are nearly parallel, the 

 greatest depth of the fin being r ,'„ inch. The posterior margin is 

 truncated, and slightly emarginate, so that the posterior inferior angle 

 projects a little further back than the posterior superior. The 1 

 which should form the upper and lower angles of the fm are abnorm- 

 ally short, and, along with the rays forming the middle of its expan , 



