APODALS 



WITH ARTICULATED FIN-RAYS. 



Family GYMNOTID^. 



Form eel-like, with a round back and no dorsal fin ; a greatly- 

 developed anal fin, which either extends to the point of the tail or 

 leaves the extremity of that member free. Teeth present or want- 

 ing on the premaxillaries, the mandible and palatines. None on 

 the vomer. The scapular ring attached to the head. From the 

 fifth vertebra onwards, the belly is enclosed by distinct ribs, which 

 in many species are perceptible through the skin. They have . 

 csecal stomachs, and also pancreatic ceeca. Their ovaria are sac- 

 shaped, and the eggs are discharged in a manner widely different 

 from that of the eels. The anus, with a genital papilla behind it, 

 is situated on the pectoral girdle, or still further forwards between 

 the limbs of the mandible. The anterior small swim-bladder placed 

 under the second, third, or fourth cervical vertebra, is of a pear-like 

 form, or heart-shaped, and is double. The outer one is thick, white, 

 and easily torn ; the iianer one is transparent, full of a gelatinous 

 fluid, and lies loose within the outer one. This anterior bladder is 

 connected with the ossicles of the acoustic organ. It is attached to. 

 the single or simple second bladder by a slender cord, which is 

 divided and suspended along with the stomach by an associated 

 ligament. I consider that the anterior double-bladder belongs to the 

 acoustic apparatus, and corresponds with the membranous labyrinth 

 of more highly-organized mollusks.* 



The family of Gymnotidcc were placed with the Ajwdes merely 

 on accouut of the negative character of the want of ventral fins ; 

 but, nevertheless, though they do not belong to that group, yet 

 they may stand either before or after them. Fishes which have 

 perfect ventral ribs, branching or jointed fin-rays, a twofold swim- 

 yiadder, the anus situated very far forward, even so far as to 

 be under the chin, cannot be placed among Apodals, destitute of ven- 

 tral ribs, with only simple fin-rays, no twofold swim-bladder, and 

 the anus either in the middle of the length, or far backwards to- 

 wards the tail. The GymnotidtB in fact form a proper family, and 

 as such represent the sub-order of Apodals. 



As in all classes of animals, so in fishes, we observe certain types 

 of form. One of these types is the elongated, vermicular shape, 

 which is exhibited in the lowest stage of structural development by 

 the Cyclostomes. These have been considered as representing the 

 foetal stage of the Selachians ; and in like manner must the Apodals, 



* See "/. Riinhardt von die Schu-imhlase der Oymnotini, Wieyman's Archiv.fur 

 1854," p. 159. 



