MYOLOGY OF FISHES. 211 



superficial muscle, arising from the terminal aponeurosis of the 

 'lateral muscle,' expands and separates fan-wise, fig. 131, z, to its 

 insertion into the bases of the caudal rays. The deeper-seated 

 fascicles are exposed by the removal of the foregoing and their 

 aponeurotic origin, and arise from the coalesced terminal centrums 

 of the caudal vertebrae, to be inserted further from the basal joints 

 of the rays, and more advantageously for effecting the movements 

 which alter the spread of the tail-fin. Slender longitudinal mus- 

 cles, svpra-carinales, extend along the mid-line of the back from 

 the occiput to the first dorsal, and along the interspaces of the 

 dorsal fins in the Cod : similar muscles, fig. 131, u, extend from 

 the last dorsal to the caudal fin in the Perch ; and infra-cari- 

 nales, ib. v, extend from the anal to the caudal along the keel of 

 the tail. In the Gymnotus the supra-carinales form a single pair, 

 which extends from the occiput to the end of the tail. The modi- 

 fied cranio-dermal spines, which constitute the oval sucking-disc 

 of the Kemora, have a complex series of minute muscles, which 

 raise or depress the transverse lattice-work ; and thus become the 

 means of giving the little feeble fish all the advantage of the rapid 

 course of the whale or the ship to which it may have attached 

 itself. The muscular and membranous webs of the coalesced pec- 

 torals and ventrals of the Lump-fish, form a sucker on the oppo- 

 site surface of the body, by which it may safely anchor itself to the 

 rock, in the midst of the turbulent surf or storm-tossed breaker. 



There are many modifications of the muscular system in the 

 orders at the two extremes of the class. 



The segmental disposition of the muscular masses is most 

 simple, most distinct, most like the annulose type, in the Cyclo- 

 stomi : yet it is considerably specialised for the due working of 

 the suctorial apparatus. In the Lamprey, fig. 138, slips are con- 

 tinued or derived from the anterior part of the myocommas, for 

 drawing back, bending in different directions, and expanding the 

 mouth. Of these, the superior, e, is inserted into the cartilage, 

 fig. 24, 20 ; raises and fixes it, giving a fulcrum and favourable 

 direction for the muscle, fig. 138, b, which directly retracts and 

 raises the sucker, a : the inferior slip, f, is inserted into the pro- 

 cess, fig. 24, q, and into the lower border of the gristly base of the 

 sucker, ib. 22 : it retracts and depresses the sucker. An interme- 

 diate lateral slip, inserted a little higher upon the margin of q, fig 

 24, retracts and draws outward the sucker. All these retractors 

 co-operating, serve to expand the sucker ; or, if duly antagonised 

 by the sphincter oris, pull back the object seized by the sucker, or 

 draw the body of the fish towards it, according to the fixed point. 



p 2 



> 



