THE NATURE OF THE SPINES IN 

 CATFISHES 



By H. D. Reed and T. J. Lloyd, 

 Zoological Laboratory, Cornell University. 



Anyone who has handled catfishes, dead or alive, is 

 probably painfully aware of the presence of heavy and 

 sharp spines in the dorsal and pectoral fins. In the fol- 

 lowing paragraphs an attempt is made to explain briefly 

 the morphologic nature of these spines; that is, how do 

 they compare with the more flexible fin supports and 

 with the spines of other fishes? 



The fin is to be looked upon as an extension of the 

 general integument of the body. In nature it is precisely 

 as if the skin of the back of the hand were pinched and 

 drawn away from the surface. The web of the fin thus 

 constituted becomes useful as a balancer, propeller, or 

 rudder by virtue of its flexibility and consequent freedom 

 of movement and at the same time has the possibility 

 of a certain amount of rigidity. All these characteristics 

 are imparted to the fin by its inner supports called fin- 

 rays, to which group of structures the fin-spines belong. 



The nature of any type of fin-spine is better appreci- 

 ated after a review of the more common and more primi- 

 tive fin supports, namely, the soft rays. This kind of 

 ray is most numerous in fishes and because of its soft 

 or flexible state it receives its designation. Its role in 

 the fin is that of a skeletal support to the fin-web only. 

 The origin and homology of the soft rays have been 

 traced by Goodrich 1 , Harrison 2 and others, and may, there- 

 fore, be omitted here. Much more desirable is a knowl- 

 edge of the simple structure of a soft ray. In this con- 

 nection there are two features to be noted. First, rays 

 of this type are always dichotomously branched. The 

 base of the ray is heavy and solid, but soon divides into 



1. Goodrich, E. S. Jour. Mic. Science, vol. 47, 1903. 



2. Harrison, R. G. Arch. f. Mik. Anat vol. 42, 1893. 



