630 NATtJEAL HISTORY OF AQUATIC ANIMALS. 



191. THE EEL— ANGUILLA VULGARIS. 



Classification. — There is no group of fishes concerning the classification and history of 

 which there is so much doubt as the Bel family; an infinite number have been described, but 

 most are so badly characterized or founded on individual or so trivial characters that the majority 

 of ichthyologists will reject them.' 



In his "Catalogue of the Pishes in the British Museum" Dr. GUnther has claimed to retain 

 those as species which are distinguished by such characters that they may be recognized, though 

 he remarks that he is by no means certain whether really specific value should be attached to 

 them, remarking that the snout, the form of the eyes, the width of the bands of teeth, etc., are 

 evidently subject to much variation. In his more recent work he remarks, "Some twenty-five 

 species of Eels are known from the coast waters of the temperate and tropical zones." 



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 dift'erent 

 forms merge into one another with almost imperceptible gradations. In his monograph of the 

 family of anguilliform 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. Gtinther, 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 specific characters? In 

 this matter I have followed the suggestions made with such great force by M. Siebold in his 

 ' History of the Presh-water Pishes of Central Europe.' This accomplished naturalist has shown 

 that the relative proportions of the different parts of the body and the head vary considerably 

 in fishes of the same species, in accordance with certain physiological conditions, and that conse- 

 quently 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 Oonger and Anguilla has 

 fully convinced me of the justice of this observation of Siebold ; for the extreme variability of 

 proportions forbids us to consider 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 interest- 

 ing since albinism has hitherto been regarded as a very exceptional phenomenon in the group of 

 fishes. This also occurs in the SymbrancMdm. I have recently shown it in a specimen of Monop- 

 terus 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 partial 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 



' Gt)NTHBR: Catalogue of the Fishes in the British Museum, viii, p. 24. 



» Comptes-rendus of the Academy of Sciences, Paris. ' 



