72 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



T). dareste's views. 



Other recent writers have cut the knot by combining all of the eels into 

 three or four, or even into one, species, and it seems as if no other course 

 were really practicable, since the different forms merge into one another 

 with almost imjierceptible gradations. In his monograph of the family 

 of Anguilla-formed fishes* M. C. M. Dareste remarks : 



" Dr. Giinther has recently published a monograph of the apodal fishes 

 in which he begins the work of reducing the number of specific types. 

 The study of the ichthyological collection of the Paris Museum, which 

 contains nearly all of Kaup's types, has given me the opportunity of 

 completing the work begun by Dr. Giinther, and of striking from the 

 catalogue a large number of nominal species which are founded solely 

 upon individual peculiarities. 



" How are we to distinguish individual peculiarities from the true spe- 

 cific characters ? In this matter I have followed the suggestions made 

 with such great force by M. Siebold in his History of the Freshwater 

 Fishes of Central Europe. This accomplished naturalist has shown that 

 the relative i)roportions of the different parts of the body and the head 

 vary considerably in fishes of the same species, in accord ance with cer- 

 tain i)hysiological conditions, and that consequently they are far from 

 having the importance which has usually been attributed to them in 

 the determination of specific characters. 



" The study of a very large number of individuals of the genera Conger 

 and AnguiUa has fully convinced me of the justice of this observation 

 of Siebold ; for the extreme variability of proportions forbids us to con- 

 sider them as furnishing true specific characters. 



" I also think, with Siebold, that albinism and melanism, that is to say, 

 the diminution or augmentation of the number of chromatophores are 

 only individual anomalies and cannot be ranked as specific characters. 

 Eisso long since separated the black congers under the name Murcena 

 nigra. Kaup described as distinct species many black Anguillas. These 

 species should be suppressed. I have elsewhere proved the frequent 

 occurrence of melanism and albinism more or less complete in nearly all 

 the types of fishes belonging to this family, a fact especially interesting 

 since albinism has hitherto been regarded as a very exceptional phe- 

 nomenon in the group of fishes. This also occurs in the SymhrancMdce: 

 I have recently shown it in a specimen of Monopterus from Cochin China 

 presented to the museum by M. Geoffroy St. Hilaire. 



"I must also signalize a new cause of multiplication of species; it is 

 j)artial or total absence of ossification in certain individuals. This 

 phenomenon, which may be explained as a kind of rachitis (rickets), 

 has not to my knowledge been noticed, yet I have found it in a large 

 number of specimens. I had prepared the skeleton of a Conger of medium 

 size, the bones of which are flexible and have remained in an entirely 

 * Comiites rendus of the Academy of Scieuces, Paris. 



