CHAPTER IV. 



MINOR ABNORMALITIES. 1 



I. Hermaphroditism, ... p. 46 



II. Abnormalities affecting skull or vertebral column. 



(a) Shortening and curvature of the snout; the pug-headed condition, - - p. 48 



(b) The round-headed condition, - p. 50 



(c) Defects of the lower jaw, - - p. 51 



(d) Hump-back, twisted body, and allied conditions, - - - p. 51 



(e) Local reduplication and deficiency of the notochord, - - p. 54 



III. Abnormalities affecting fins. 



(a) Excess, - - • p. 54 



(b) Defect, ----- - p. 55 



(c) The so called " tailless " condition, - - - - - - p. 56 



IV. Abnormalities of coloration. 



(a) In fishes generally, - - ------- p. 56 



(b) In flat-fishes, associated with certain other defects, - - - - p. 56 

 V. Parasitism, ------------ p. 59 



VI. Pathological conditions of the ovum or early embryo, - - - ■ - p. 60 



VII. Abnormalities having reference for the most part to single organs, - - - p. 61 



HERMAPHRODITISM. 

 Under this heading we have to deal almost entirely with true hermaphroditism, since the Teleosts 

 (which provide the vast majority of instances) do not, on the whole, possess accessory genital 

 structures which are peculiar to either sex. Among other fishes, the only instance of spurious 

 hermaphroditism I have come across is provided by the adult male skate described by Matthews 

 {151) as possessing an oviduct on the left side. The specimen measured over two feet in length and 

 had practically perfect glands and ducts of the male type on either side. In addition there was a 

 Mullerian duct of full adult size on the left side. This duct was furnished with a large oviducal 

 gland and contained numerous living spermatozoa in its anterior (Fallopian tube) portion. It may 

 he noted in this connection that the male Raia elavata is occasionally found with teeth as much 

 blunted as those of the female (Day 5J, II. p. 344). 



True hermaphroditism, normal. As is well known, the condition occurs normally in a number 

 of fishes. Following Howes (101) with slight modification, we may distinguish three types of 



1 The following paragraph from Stoddart ("39 p. 75) is worth quoting at this stage. It shows the frequency with which 

 abnormalities of many kinds occurred in trout from Scottish waters before artificial hatching was practised, and at a time 

 when the amount of sewage pollution must have been vastly less than it is now. 



" We have caught them hump-backed and covered with sores, blind of one eye, wanting a gill or a fin and crooked up in 

 all shapes. On the Tay we once took an individual with a short round upper head like that of the bull-dog and the lower lip 

 projecting beyond it. We understand that a variety of this kind is to be found in Loch Dow in Inverness-shire. On the 

 Water of Leith we saw a friend capture three successively out of one stream all of which wanted the tail ; this defect was 

 most probably occasioned in winter, the water from which they were taken happening to be extremely shallow and the frost 

 before being somewhat severe." 



