MORMYEID^E. 



27 



Mormyrus hannume 12-13 + 7 + 30 = 49-50. 



cascliive 13 + 10 + 31-32 = 54-55. 



Hyperopisus bebe 15-16 + 4-6 + 35-38 = 55-59. 



Gymnarclms niloticus 45-47 + 67-75 = 114-120. 



The Mormyrids are remarkable for the enormous development of the brain and for 

 the problematic organ which surmounts it * ; also as being among the few fishes in 

 which an electric organ has been discovered f. This organ, situated on each side of 

 the caudal region, is derived from the muscular system and is of feeble power ; it was 

 long considered as " pseudoelectric." 



The natural affinities of this family appear to be with the most generalised Teleosteans 

 (Elopida? and Albulidae). Dr. Ridewood's careful study of the skull has not confirmed 

 the view of a particularly close relationship to the Albulidae, which I formerly advocated. 

 There is no relationship with the Esocidse, near which the Mormyrs have been placed 

 by several authors, and nothing to justify the term " Nil-Hechte " (Nile-Pike) which 

 has been bestowed on them by German writers. 



Fig. 7. 



Tail of a Mormyrus, with the skin removed to show the electric organ, in the form of two series of 

 oblique band-like plates (modified muscles). After G. Eritsch. 



Over 100 species are known from the fresh waters of Tropical Africa and the Nile, 

 and are referred to two subfamilies and ten genera, seven of which are dealt with in 

 this work. 



Very little is known of the habits of these fishes. Prof. G. Fritsch, of Berlin, durino- 

 his stay in Egypt for the purpose of experimenting on electric fishes, observed that they 

 perish very rapidly when removed from the river, and he had the greatest difficulty in 

 keeping some alive in an aquarium for two or three days. Capt. Flower has recently 



* Cf. Oeffinger, Arch. f. Anat. u. Physiol. 1867, p. 713, and Boulenger, Poiss. Bass. Congo, p. 52. 

 t Cf. Babuchin, Arch. f. Physiol. 1877, p. 250 ; G. Fritsch, Sitzb. Ak. Berl. 1891, p. 941 ; and Ogneff, 

 Zeitschr. wiss. Zool. lxiv. 1898, p. 565. 



e2 



