84 Memoir Sears Foundation for Marine Research 



persons who have come in contact with them in one way or another. The following is an 

 interesting first-hand account of such an experience in Australia. 



Whilst wading at Gunnamatta Bay I trod on an electric ray and it was as if a large hand clutched 

 my foot and ankle. I netted the specimen and put it on a sand bank. Here I noticed a black leech between 

 its eyes, and in trying to knock this off with my net got a more severe shock, which so suddenly contracted 

 the muscles of my arms and legs that I leapt a foot in the air.^* 



Indeed, the shock from a large one in rested condition is strong enough to knock 

 down and temporarily disable a full-grown man (p. 102). So Electric Rays might even 

 be dangerous to bathers who accidentally step on them as they lie buried in the sand 

 in the shallow water of regions where the larger sizes are common enough for this to 

 be a likely occurrence. 



It has been stated that Torpedoes are immune to their own shocks. But it seems 

 that they are not wholly so, for it has been observed that the discharge is accompanied 

 by a slight and brief muscular contraction, as noted before (p. 82), this apparently 

 resulting from the reception of its own discharge. 1^ It has been argued that their ap- 

 parent immunity results, in reality, from the weakening of the electric discharge as 

 it passes through the water. ^^ 



The requirement that the recipient of a shock must complete the circuit by making 

 contact with the fish at two points, whether directly or indirectly, is fulfilled in the 

 normal life of the Ray by means of the surrounding sea water. This has been illustrated 

 experimentally with the recording of the shock by telephone, one pole of which is in 

 metallic contact with the Torpedo, the other pole (also metallic) in the water at a dis- 

 tance not greater than 20 cm (8 in.) from the fish." It is only if an Electric Ray is out 

 of water, as when lying on the dry planks of a dock, that the mechanical two-point 

 contact is requisite. And even in such cases it has been found that "quite a powerful 

 sensation of numbness can be produced through the medium of a stream of water, that 

 is to say, by pouring water onto a living fish."^^ 



The disabling effect that shocks by Torpedoes may be expected to have on small 

 animals that may come in contact with them has given rise to a general belief that 

 electric organs of the Torpedo normally serve a defensive purpose. Although it has 

 been questioned recently whether the organs are of much importance in this respect, ^^ 

 it has been observed in the Naples Aquarium that crayfish, crabs, and cephalopods are 

 greeted by discharges if they chance to touch a Torpedo marmorata lying on the bottom. 

 Indeed, one was seen to drive off a large octopus in this way.^* However this may be, 

 it seems probable that the shocks do serve more or less to stun the prey, for wholly 

 uninjured fishes, so large that it seems hardly conceivable that they could have been 

 swallowed unless they had been rendered helpless beforehand, have been found in the 



iS. Whitley, Fish. Aust., j, 1940: 165. 



19. Jobert and Jolyet, Trav. Lab. Soc. sci. Arcachon (1895), 1896: 57. 



20. Schonlein, Z.Biol., 31 (N. S. ij), 1895: 512. 21. Schiinlein, Z.Biol., 31 (N. S. Jj), 1895: 450. 



22. Norman and Fraser, Giant Fishes, 1937: 65. 



23. Liibbert and Ehrenbaum, Handb. Seefisch. Nordeurop., 2, 1936: 317. 



24. Schonlein, Z.Biol., 31 (N. S. 13), 1895: 450, 453. 



