THE GYMNOTID EELS OF TROPICAL AMERICA. 191 



swim almost entirely with the long anal fin, the pectorals being used largely to 

 guide the fish. All of this series were dead when visited the following morning. 



Series 4- Injury in Ventral Quarter. 



From the anal fin and anal muscles of ten specimens V-shaped pieces about 

 20 mm. wide at the base were cut, so that the point of the "V" pierced the body 

 cavity for some five millimeters. These when dropped into the water made some 

 rather feeble efforts to right themselves. 



Seven of them died during the two hours they were observed and the other 

 three were found dead the next morning. 



Series 5. Surface Injury, Dorsal Quarter. 



Wedge-shaped pieces about 20 mm. long and 5 mm. deep were cut from the 

 middle of the back in the region above the pectorals from five specimens. The 

 tissue thus removed included only skin, scales and dorsal muscle. These injuries 

 bled considerably more than those of Series 2, the entire surface of the wound being 

 covered with blood shortly after the cut was made, and blood continued to ooze 

 from the wounds for about five minutes after each fish was returned to the water. 

 These injuries were apparently of little consequence to the fishes, for they swam 

 about as actively and in the same fashion as their uninjured associates. On the 

 following morning all were found alive and active. In each case the wouikJ had 

 begun to heal. y^ 



Series 6. Deep Injury, Dorsal Quarter. 



From the same region as that operated upon in Series 5, wedge-shaped pieces 

 about twenty millimeters long, and deep enough to remove a portion of the vertebral 

 column, were cut from each of ten fishes. These injuries were such as to sever the 

 vertebral column, the spinal cord and the dorsal blood vessel, the wound thus 

 produced bleeding considerably. The injured fish when returned to the water 

 made disconcerted efforts to swim but soon settled to the bottom. Here they 

 maintained a half normal position or lay completely on one side. Blood continued 

 to ooze from their wounds for about half an hour after the operation and when 

 they were left at the end of an hour and a half most of them seemed almost dead. 

 None of this series were alive next morning. 



In the above experiments the injuries which produced death during the first 

 twenty-four hours after the operation were those inflicted in Series 3 (the removal 

 of all of the body caudad of the viscera and air-bladder) , Series 4 (the opening of 

 the body cavity and air-bladder), and Series 6 (the severing of the dorsal artery, 

 the spinal cord and the vertebral column in the suprapectoral region). Naturally, 

 specimens regenerating such injuries were not found among the collections. 



The injuries of the other three series, Series 1 (loss of the entire caudal append- 

 age), Series 2 (removal of the entire caudal appendage plus a small portion of 



