126 LF.CTUKE V. 



A series of developments may be traced from the primitive form of 

 the appendage, as a simple plate, spine, or ray, through the many- 

 jointed single ray in the Lepidosiren and the bifurcate jointed ray in 

 the Amphiuma didactylum, up to the wing of the Bird and the arm 

 of the Man, without the essential nature of the part being lost sight 

 of ; for all these forms of the pectoral member are, in their ultimate 

 or general homology, ' diverging ' or ' radiated appendages ' of a 

 hfemal arch ; but not ' ribs,' nor ' vertebrce.' We may further define 

 the fore-limb, wing, or pectoral fin to be the radiated appendage of 

 the arch called ' scapular,' and this to be the ' ha3mal arch of the occi- 

 pital vertebra.' 



There remain to complete the analysis of the skeleton of the Cod, 

 here taken as a type of Osseous Fishes, the bones of the ventral i^air 

 of fins and the cranial j)arts of the dermal skeleton. The rays of 

 the ventral fin are supported by two bones, which represent the 

 lower portion of an imperfect inverted or haemal arch ; each bone is 

 a sub-triangular bifurcate plate in the Cod tribe, with its apex an- 

 terior and superior, joined by ligament to the same part of the cor- 

 resj)onding bone, and suspended beneath the coracoid arch. To the 

 outer part of the base of each suspending bone the rays of the ventral 

 fin are attached without the intermedium of any series of short 

 ossicles ; in fact, the representatives of tarsal, tibial, and femoral 

 bones are wanting in all fishes, and the lower half of the pelvic arch, 

 {ov ihe, j^tibic bones, Jig. 19. 63), and the peripheral and essential parts 

 of the fin, the metafarso-phalangeal pointed rays (ib. 70), alone repre- 

 sent the hinder or lower locomotive member in fishes. In Acan- 

 thopterygian Fishes one or more of the anterior rays of the ventral fin 

 may be hard unjointed spines, as in the other fins ; in the Malacopte- 

 rygians all the ventral rays are soft, multi-articulate, and bifurcate. * 



In no fish is this incomplete pelvic arch directly attached to the 

 vertebral column. If we may judge from the position in which the 

 ventral fin appears, in the development of the embryo fish, as a little 

 bud attached to the skin of the belly, and from the fact that all the 



* Ichthyologists avail themselves of the number and kind of rays in the several 

 single and parial fins to characterise the species of fishes, and adopt an abbreviated 

 formula to express those characters : thus Mr. Yarrell (xxxix. i. p. 4.) uses the fol- 

 lowing with reference to the Perch : — d. 15, 1 + 13 : p. 14 : v. 1 + 5 : a. 2 + 8 ; 

 c. 17 : which signifies that p., the dorsal fin, has in the first fin 15 rays, all spinous; 

 in the second fin, 1 spinous + (plus) 13 rays that are soft, p., the pectoral fin, 14 

 rays, all soft, v., the ventral fin, with 1 spinous ray + 5 that are soft, a., the 

 anal fin, with 2 spinous rays + 8 that are soft, c, the caudal fin, 17 rays. The 

 formula of the fin-rays in the Haddock is : n. 15, 21, 19 : p. 18: v. 6 : a. 24, 18 : 

 c. 44. : i. e. all the rays are soft, and there are 15 rays in the first dorsal, 21 in the 

 second dorsal, and 19 in the third dorsal ; 18 rays in the pectoral fin ; 6 rays in the 

 ventral fin ; 24 rays in the first anal, and 18 in the second anal fins ; and 44 rays 

 in the caudal fin. 



