III. COTTOIDS OP NORTH AMERICA. 29 



the dorsal line down to the ventral line, are characterized by inflexions or curves, 

 forming sometimes gentle undulations and sometimes angles more or less acute. 



Now these angles, these curves, delineate organic regions in the body, and, 

 having satisfied ourselves that a wide field of inquiries and philosophical deductions 

 is connected with the morphology of the muscular system, we did not hesitate in 

 giving figures of the general appearance of the fleshy parts in a species of the genus 

 Cottus. If, instead of reproducing over and over the same figure, anatomists had 

 given us each time another, we would possess now very important data for the 

 understanding of the muscular masses, not only in the class of fishes but also in 

 vertebrata generally. Fishes, reptiles, birds, and mammals being constructed upon 

 the same plan, there is a morphology to be traced throughout those four classes ; 

 and, besides, each class has to be thoroughly investigated in this respect. 



As we are not prepared, on account of the scarcity of materials, to say anything 

 general on the class of fishes, and as it is not within the limits of this work to enter 

 into such inquiries, we shall limit ourselves to a mere sketch of our views. 



In C. ILSCOSUS (Plate III. Fig. 3), the muscular flakes of both sides are seen to 

 meet along the back under the shape of an acute angle directed backwards, indicat- 

 ing the dorsal line. The region of the bade is indicated by another bending of the 

 flakes forwards. The next curve, the convexity of which is directed backwards, 

 takes place on the line of separation of the back and abdominal region (Fig. 1). 

 The abdominal reyion itself is marked by a very open curve, convex forwards, 

 extending down till another smaller curve appears, separating the abdominal from 

 the ventral region on which the flakes gently undulate (Fig. 2). 



On the tail, or caudal region, the bending of the flakes is more uniform than on 

 the trunk; but the tail, it must be remembered, is a mere appendage, although an 

 organic region too. This region is always much developed in osseous fishes as well 

 as in many cartilaginous, continuing the trunk backwards. In some cartilaginous 

 fishes, it is very slender and filiform. In some reptiles it vanishes completely; in 

 birds it is most diminished, and in many mammals it reappears under a very dis- 

 proportionate shape, whilst in others it again loses its importance. The muscular 

 system of that region is accordingly liable to corresponding variations. 



The morphology of the caudal region constitutes no serial law, whilst the mor- 

 phology of the muscular flakes, along the trunk in fishes and the localization of 

 the muscular masses in the other classes of vertebrata, will illustrate an organic 

 gradation. 



The fins and rays are put into motion by sets of muscles independent of the 

 flakes, the description of which cannot find any place here. We would only glance 

 at the branchiostegal apparatus (Plate III. Fig. 4), the rays of which are dis- 

 tended or retracted by transversal, thin muscular bands, attached above at the 

 inner surface of the opercular, uniting below with the transversal fibres of the 

 isthmus. Fig. 2 also exhibits the general outline of the glosso-hyoidean muscle, 

 much developed in Cottoids. 



Between the skin and the flakes there exists a thin layer of muscular fibres, the 

 muscles of the skin. In C. viscosus they cover completely the flakes all along the 

 region of the back, the fibres running from one side to the other in passing unin- 



