840 



SCAXDINAVIAX FISHES. 



The spina] column is also marked b}^ its weak 

 ossification. The neural arches proper (Owen's neurapo- 

 physps) are persistently cartilaginous in most of the 

 abdominal vertebra}, and the bases of their neural 

 spines are united to the bodies of the vertebraj only by 

 a suture or, in young specimens and in the anterior 

 part of the column, by a mobile articulation. In the 

 forepart of the skeleton these spines are also but loosely 

 united to each other, the right to the left in each ver- 

 tebra, and with the hind surface of each base articulates 

 a rib-like muscular bone, directed outwards, backwards, 

 and upwards (Owen's diapophysis). In the posterior 

 part of the abdominal region the cartilaginous neural 

 arches disappear, the bases of the neural spines take 

 tiieir place and develop a firmer osseous connexion with 

 the bodies of the vertebra?, the neural arches thus 

 formed being strengthened at the same time by the 

 coalescence of the spines on each vertebra. The diapo- 

 physes decrease in length, and disappear near the caudal 

 region; but simultaneously there appear, though with 

 only slight development, the knob-shaped articular pro- 

 cesses {zyfiapophyses) that in the Cyprinoids are gene- 

 rally so prominent on the anterior abdominal vertebne, 

 (me pair in front of and one pair behind the neural 

 arches, \vhich are here most constant in the caudal 

 region, though even there they may be wanting. The 

 development of the hiBmal arches proper (Owen's hcem- 

 apophyses) takes the reverse direction. It advances from 

 the front of the body to the posterior part thereof: on 

 the first vertebra they are scarcely distinguishable ex- 

 ternally from the body of the vertebra; on the second 

 vertebra they are distinct protuberances, one on each 

 side of the lower part; on the third each of them is 

 furnished with a rib; and they thus continue to in- 

 crease until, near the caudal region, a succession of 

 haemal spines appears, each bearing a pair of ribs on 

 the hind surface of its top, while the hiemal spines of 

 each vertebra approach each other at the top, forming 

 (usually on the last six abdominal, as well as on the 

 caudal vertebra;) a closed ha?mal arch. On the same 

 vertebra? as the ha?mal spines, there also appear lower 



articular processes similar to the upper. The ribs are 

 .slender, in sharp contrast to those of the Cyprinoids. 



In the shoulder-girdle, the structure of which is 

 else the same as in the preceding family, the clavicle 

 is tliiii and liroad, with the upper arm comparatively 

 short, and the postclavicle consists of three, sometimes 

 four parts, namely two (sometimes three) upper, thin 

 and flat, and one lower, pointed and rib-like. This 

 division of the postclavicle recurs in the Herrings. 



The pelvic bones are simple and triangular, with- 

 out the indentation in front, and with only a rudiment 

 of the process behind, which we have seen in the Cy- 

 prinoids. But remnants of the older piscine types' 

 radialia (mobile basal bones of the ventral rays) and also 

 of the true pelvis of the said types, have been detected 

 in the Forell stage by Davidoff". 



The intestinal canal is rather simjde and short, as 

 in most predatory fishes, its entire length, when ex- 

 tended, being about equal to the length of the body or 

 somewiiat less than the latter. The stomach is only 

 faintly marked oft" from the rest of the canal; but a 

 remarkable point is the thickening of its walls which 

 attends a diet of mollusks or other testaceans''. This 

 thickening has been most frecjuently observed in the 

 so-called Gillaroo Trout of Ireland, a form which has 

 hence been named by Gunthek Salmo stomachicus ; but 

 it may also be observed in common Lake Trout". The 

 pyloric part is directed forwards, as well as the be- 

 ginning of the true intestine (duodenum), which is ex- 

 ceedingly well furnished with cffical diverticula. These 

 appendages, however, vary considerably both in size 

 and number, from about 30 to nearly 100. They are 

 generally most numerous in the Salmon proper, where 

 Kroyer'' has counted 96, though the usual number in 

 this form is between 50 and 70. In the Trout that 

 migrate to salt water, the usual number is al)out the 

 same; but in those that live exclusively in fresh water, 

 it is generally less, about 30 — 50. Thus in dift'erent 

 specimens of Trout 29 — 69 pyloric appendages have 

 been counted'. After the duodenum has advanced al- 

 most to the diaphragm, the intestine abruptly bends 



" Morph. Jahrb., XVI (1880), p. 464, faf. XXI, fig. 5. 



' According to Day a seagull at Hunter's Museum was fed for some time on corn, and the muscular layers of its stomach were 

 thereby thickened as in a crop; and from Holmgren's experiments on pigeons at U])sala it appeared that the muscular layers in their crop 

 were reduced by a flesh diet. 



° It is further known that a nmlhiscous diet gives the body of the Salmons a singular, orange ground-colour. 



* Danm. Fiske, BH. 2, p. 558. 



^ Day, British Salmonichv, p. 188. 



