THE GYMNOTID EELS OF TROPICAL AMERICA. WN 7/2) 
as those collected by Dr. Eigenmann. In no ease were the females at this time so 
full of eggs as to be distended. 
MUTILATIONS AND REGENERATION. 
The specimens of Gymnotide in different collections show an unusual amount 
of mutilation and regeneration. This condition is undoubtedly in part due to 
their peculiar anatomy and shape. It may be recalled that they are all slender, 
elongate fishes, with the visceral anatomy occupying a relatively small portion of 
the fish just behind the head. The viscera, except the air-bladder, are so closely 
packed that the mass occupies a space a little longer than the length of the head. 
The compound air-bladder varies in size and shape in the several species. It lies 
just below the spinal column on the posterior portion of the body cavity and 
extends caudad to between the anterior third and the middle of the body. The 
position of the anus is also noteworthy. The alimentary canal after several turns 
bends down and runs forward along the floor of the body cavity and terminates 
below the head or below the base of the pectorals. Back of the body cavity the 
body tapers off gradually. The dorsal region bears no fins, hence the name, 
Gymnotide. Ventrals are also wanting. All species, however, have small fan- 
shaped pectorals and a very long anal fin. The anal begins in the pectoral region 
and extends caudad for the greater length of the fish. The number of rays in this 
fin varies greatly among the different species and also among individuals of the 
same species. In one species, at least, the number of anal rays may exceed five 
hundred (Rhamphichthys rostratus). The species of one subfamily, the Stern- 
archine, have a caudal fin. The tail of the other species tapers into a slender, 
cylindrical, caudal appendage. 
Mutilation and the attendant regeneration are of general occurrence through- 
out this family. Many of the accounts of the Gymnotide note either in passing or 
even in detail, cases of regeneration in the caudal and anal regions. Nineteen of 
the twenty-seven species of this family are known to have regenerated lost portions. 
The present account consists of three parts: the first deals with regeneration in 
general in this group, and is based both on the collections examined and on the 
cases recorded by others; the second relates to special collections of three species; 
and the third gives an account of some experiments carried on during the Gimbel 
Expedition. 
Part I. REGENERATION 'N GENERAL. 
The first table lists all of the species of the Gymnotidw and indicates those 
known to have regenerated lost parts. Whenever specimens were at hand showing 
injury and regeneration, the word “specimens’’ follows, while cases not examined 
by myself are referred to the author mentioning them. Reference to several 
interesting regenerations recorded for species of which mutilated specimens were 
examined by myself is omitted from this table. It demonstrates the general 
oecurrence of regeneration throughout the family, regeneration being recorded for 
