112 THE ELASMOBRANCH FISHES 



flexor (f.e.) differs in that its point of origin is far removed from that of the 

 internal flexor (/.?".). 



In the rays, where the skeleton of the fin is much more complex, the muscles 

 have undergone a relatively high degree of specialization. In figure 114a of 

 Raja clavata the adductors (ad.) are shown on the ventral side as diverging 

 fibers passing toward the sac. Surrounding the sac is the large compressor, a 

 part of which also appears in dorsal view {cp., fig. 114b). The large dilator 

 (dl.) in the same view is divided into a ventral and a dorsal part, the latter 

 being very heavy. Continuing from this muscle on the dorsal side is the large 

 external flexor (f.e.) and at its sides is the margin of the adductor seen also in 

 ventral view. 



ELECTRIC ORGAN IN ELASMOBRANCHS 



One of the most highly specialized organs found in the animal kingdom is 

 present in the rays. This is the electric organ by means of which electric shocks 

 can be generated. While this organ is found in its perfected form in Torpedo, 



/Ids. 



Fig. 115. The relation of the electric organ to the muscles, Eaia batis. (From Ewart.) 

 ds., electric discs; mf., muscle fibers. 



it is also present in the genus Baja. In Torpedo it consists of vertically placed 

 discs located on the dorsal part of the pectoral fin. In the rays, on the other 

 hand, it is made up of a series of cones located in the tail. 



Electric Organ of Rays 



The electric organ of the ray is spindle-like and extends throughout the greater 

 length of the tail. It is spindle-shaped, however, only in part. While it tapers 

 gradually at both ends, in the middle region it is not always cylindrical, since 

 it is subject to pressure from the surrounding ligaments, muscles, and the 

 vertebral column, resulting often in deep grooves in the organ. (Ewart.) 



Figure 115 shows the relation of the electric organ of the ray to the sur- 

 rounding muscular tissue. From this it is seen that the organ is continuous 

 with the lateral row of muscle cones. In fact it is clear that the organ itself is 

 formed as a series of cones altogether similar to those of the muscle, with the 

 single exception that the direction of the muscle fibers (mf.) in the muscle is 

 more ol)lique to the myosepta than are the discs (ds.) of the electric organ. 



