190 



MEMOIRS OF THE CARNEGIE MUSEUM. 



placed in a screened portion of a second smaller trench. As this was fed from 

 the main trench, the fishes were returned to a normal environment. As the screened 

 trench was only about eighteen inches wide and two feet deep their actions were 



4 ■■^ 



Fig. 3.3. Injuries used in experiment. Stcrnopygus macrunis (Bloch and Schneider). 



easily observed. Figure 34 shows the several injuries discussed under these experi- 

 ments. Each bears the number of the series. 



Series 1. Injury to the Caudal Appendage. 



Various amounts of the caudal appendage were removed from five fishes and 

 the entire caudal appendage from three others. These, when returned to the 

 water, swam about much the same as uninjured specimens. The loss of the 

 caudal appendage seemed in no way to disturb their activity. When the appendage 

 was cut off only a tiny drop of blood came to the surface of the wound. All were 

 alive and active when observed twenty-four hours later. 



Series 2. Injury to Caudal Appendage and Caudal Region. 



Five more specimens were injured by the removal of the entire caudal append- 

 age and from ten to twenty millimeters of the caudal region of the body. These, 

 when placed in the water again, behaved much as normal fishes though they 

 seemed less incHned to swim about at first. The removal of a larger portion of the 

 caudal region was followed by the loss of a little blood, that is, the entire surface 

 of the wound was covered with blood immediately after the cut was made. This 

 blood came almost entirely from the caudal artery and spread out over the cut 

 surface, but the bleeding stopped when the specimen was placed in water. All 

 of these fishes were alive and active the next morning. 



Series 3. Diagonal Injuries. 



Five other individuals were injured by a diagonal cut which removed all of 

 the caudal region, just missing both the viscera and air-bladder. These did not 

 swim when returned to the water, but sank to the bottom, maintaining, however, 

 the normal swimming position. When disturbed they swam feebly with the 

 pectorals and the remaining portion of the anal fin, the major part of which had 

 been removed by this injury. It is well at this point to recall that the Gymnotidce 



