THE CHARACIDAE. 19 



as the primitive Ostariophysi from which the Cyprinidae (Gymnonoti) and 

 Nematognathi have been derived. These families seem to him to represent 

 three states in the evolution of Teleosteans, the Cyprinidae and Siluridae being 

 derived apparently from a common ancestor, very near the Characins, these 

 latter ranging themselves to the holostean Ganoids through the Erythrins. 

 Later Boulenger (Cambridge natural history. Fishes, 1904, p. 575) refers to 

 them as "a very generalized type, although perhaps not directly derived from 

 the bony Ganoids." The relationship recognized by him he represented as 

 follows : 



Eventognathi 



Nematognathi 



Gymnonoti 



Heterognathi 



Rowntree (Trans. Linn. soc. Lond., 1903, ser. 2, 9, p. 78) concludes his 

 extensive account of the visceral anatomy of Characins with the following 

 words: — "With the possible exception of the indications of a cellular air-bladder, 

 there appears to be nothing in the visceral anatomy of the Characinidae which 

 strengthens the deductions made from the skull as to the Amioid affinities of 

 the group. In opposition to such deductions are especially the cystoarian 

 ovaries, the asymmetric ductus pneumaticus, the presence of pyloric appendages 

 and the absence of all trace of a valvular conus and of an intestinal spiral valve." 



In view of the observations of every naturalist who has studied the Char- 

 acins, notably Boulenger with the African species, and the author with the 

 American forms, it is doubtful whether the similarity of the Erythrins with the 

 Ganoids is anything more than one of the innumerable radial adaptations this 

 plastic family has undergone. 



Radial Adaptation. 



Boulenger's remarks (Poissons bassin Congo, 1901, p. 132-135) concerning 

 the African representatives may be translated as follows: — 



This is a very natural family whose internal organization shows a great affinity with 

 the Cyprinidae but whose exterior appearance, due to adaptation to various modes of life, 

 varies so much that the beginner in African ichthyology will mistake its various representa- 

 tives as near the Salmonids, pikes, and roaches of Europe. It is also impossible to state in a 



