436 MR. J. B. SUTTON ON HYI'KRTROPH Y. [May 5, 



minds, who never come across anything out of the common but 

 thev must rack their brains to find out some useful purpose for 

 which they think the abiiorniai organ nay be ulih2ed, never con- 

 sidering for one moment the absurdity of the explanation. 



As is well known these teeth, like those of Rodents, grow from 

 persistent pulps : if from any cause their growth is unopposed, as 

 by want of antagonism between any two teeth, they grow to extra- 

 ordinary length. In the case of the Babirusa it may readily be 

 conceived that, from some cause or other, the upper and lower 

 canines failed to come into apposition either by malformation or in a 

 manner presently to be ex]dained, and as a consequence grew enor- 

 mously ; the abnormality frequently recurring, the pecuHarity became 

 transmitted to the offspring, eventually becoming perpetuated to 

 such a degree as to become a common feature in the anatomy of the 

 males of this particular species. 



Considered by itself, this isolated example perhaps does not carry 

 much weight, but the condition may be ajiproached insidiously from 

 other specimens of the Suidae. The first stage may be observed in the 

 Wild Boar (of which the dentition is represented in fig. 3, p. 437), 

 where the form and direction of the canines are peculiar. The lower 

 canine is slender when compared with the upper, is of some length, and 

 plays against the front surface of the upper one, becoming ])ointed in 

 consequence. The upper canine passes at first horizontally outwards 

 with an inchnation forwards. After clearing the outer lip, its apex 

 becomes directed upwards and inwards, describing in its course a 

 semicircle. A similar condition is seen in the Wart-hog, Phaco- 

 choerus aliani ; but the second stage is presented hy Phacoc/ioerus 

 tethiopicus, in which the canine attains considerable proportions, as 

 may be seen on reference to fig. 4 (p. 437). 



In the third step we are confronted with Babirusa, whose ex- 

 cessive canines I maintain are inherited pathological peculiarities 

 resulting from want of apposition, probably brought about in the 

 first instance as a result of malformation (see fig. 5, p. 437). 



It may, with reason, be asked, can an example be adduced of un- 

 doubted transmission of a pathological condition to the offspring so as 

 to taint an entire community ? An example offers itself in the so-called 

 Tailless Trout of Islay. A careful and detailed account of this malfor- 

 mation is given by Prof. Traquair in the .' Journal of Anatomy,' 

 vol. vi. p. 411. From this account it appears that the common 

 Trout, Salmo fario, Linn., is frequently the subject of malforma- 

 tions, of which sigmoid distortions of the vertebral column and 

 deficient development of the snout and jaws is the most common. 

 In the present case, however, it is the caudal fin which is affected 

 of all the Trout inhabiting a certain small lake. The most sahent 

 peculiarity of these Lochnamaorachan Trout is that the rays of 

 the caudal fin are abnormally shortened, coarse at the extremities, 

 and deficient as to the amount of dichotomization and number of 

 the transverse joints ; besides which they also show a tendency to 

 coalesce at their terminations. By the convergence downwards of 

 the upper long rays and upwards of the lower ones, the fiu assumes 



