52 



MINOR ABNORMALITIES HUMP-BACK, ETC. 



Erdl and Stannius. The papers by Hofer (9 6 a), Freund (70) 1 and Pellegrin (188) should also 

 be consulted. 



Not many data are available regarding twisting of the body in the early stages of fishes other 

 than the Salmonidae, but attention may be called to notes by Holt (9 7) on this condition as occurring 

 in embryos of Zoarces, and by Williamson (2 69 a) in those of the herring. Both these authors refer 

 to observations on the influence of cold in producing the condition in question. 



Structure. Hump-back and allied deformations of body or tail may be accompanied by the 

 following modifications of the vertebral column. 



(a) Coalescence or synostosis of the vertebral centra in groups of several (e.g. 2 to 6) segments, 

 while the neural and haemal spines, the muscle masses, and the spinal nerves retain their normal 

 number. An excellent example is described by Ritchie (207), and another cited by Howes (102a) 

 from Hyrtl (10%b). The specimens described by Smith (2%8a), Cobbold (41 a), and Dyce (6 la), 

 referred to above, also belong to this type. The condition is noted by Tornier (%49) as being 



characteristic of some of the races of goldfish. It is usually, 

 if not always, accompanied by increase in the transverse 

 diameter of the affected centra, which may be so great that 

 the weight of the fused centra exceeds that of an equal 

 number of normal ones (Howes 10%a). There is also 

 shortening in the antero-posterior direction, which may be 

 so extreme that four or five coalesced centra occupy less 

 than the length of two normal ones. 



(b) Simple shortening of the length of the vertebrae 

 with increase in their transverse measurements, but without 

 fusion of centra. This is said to occur in goldfish races 

 (Tornier ^49). Mr. J. Eitchie, in a note to me, states that 

 he has found a similar condition in certain fish from the 

 Firth of Forth. Lowne (IJ^G p. 122) catalogues a specimen 

 of the sole in which there is arrested development of 

 1 2 post-anal vertebrae, " the bodies of which have only 

 about half their usual length and look as if they had been 

 pressed together." Probably the condition in question 

 grades into that described under (a). 



(c) The backbone may show twisting or curvature 

 without coalescence of vertebrae. Perhaps the most striking 

 examples are those described by Howes (10a) in a sole, and 



by Storrow (%41) i Q a codfish. In both there are five sharp sinuosities. The vertebral bodies are 

 complete in number, independent, and only modified in shape so as to suit their position in the 

 curves. Howes notes the interesting point that the neural and haemal spines are altered (by 

 shortening, change of slope, etc.) so as to conform as far as possible to a normal body outline. The 

 length of the body is, however, very distinctly lessened and its dorso-ventral diameter increased. 

 A second sole described by Howes (10%a) has its vertebral column curved only in the anterior 

 region. Three distinct sinuosities occur in the backbone of a perch referred to in the same paper. 



(d) In a specimen of the sea trout (Salmo trutta) sent to the author by Henry Lamond, Esq., 

 a shallow notch in the contour of the dorsal surface of the fish behind the dorsal fin was marked 

 internally by an entire absence of one of the neural arches, and a semi-fibrous condition of the dorsal 

 portion of the succeeding myomere. None of the spinal nerves was missing. 



1 This author notices a number of other records, chiefly from papers to which I have not had access, and thereby adds 

 to the above list examples from Acanthias, Amia, Grenildbrus, Esox, Gymnotus, Leuciscus, Mormyrus, Mulhis, Phoxinus, 

 Polypterus, Tinea, and Trigla. From Pellegrin (188) we have further to add Oobitis and Scomber. Hofer quotes the 

 statement from Hubrecht (Klassen u. Ordn. 6. Abt. 1-3, p. 60), that in shark-like fishes, pathological coalescence of vertebrae 

 is commonest at the places of connection of the paired fins with the vertebral column. 



7!f- 



FIG. 6. Transverse section through posterior part 

 of body of an advanced Salmo fario embryo, showing 

 curvature and deformation due to the condition 

 described under (/). be, body cavity; df, dorsal fin ; 

 hoc, haemal arch cartilage ; int, rectum ; Ipf, left 

 pelvic fin ; mdl, dorso lateral muscle mass ; mdf, 

 small muscles connected with the dorsal fin ; nch, 

 notochord ; pfc, pelvic fin cartilage ; rpf, right pelvic 

 fin ; sc, supporting cartilage of fin ray ; sfc, spinal 

 cord ; wi, Wolffian body. 



