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Part III. — Thirteenth Animal Report 



females have a higher and broader dorsal fin than eels with the lobe-organ 

 of equal size ; and finally, — 



(5) The generally — for it is not always the case — larger diameter of the 

 eye in eels with lobe-organs. Eels with particularly small eyes are nearly 

 always females, whilst eels with a Syrski organ have generally large eyes, 

 although many female eels have also large eyes. 



Jacoby, whilst examining female eels, found certain individuals whose 

 reproductive organs were very undeveloped, and which showed distinct 

 outward differences from the ordinary female. These he regards as sterilo 

 females. The following description is taken from his article on the 1 Eel 

 Question ' : — ' In Comacchio, and doubtless wherever large masses of eels 

 ' live in brackish waters, near the sea coast, a certain variety of eel exists, 

 ' which I found were barren females of the common species. They are 

 ' female eels whose ovaries show an entirely anomalous condition. On 

 ' opening such an eel, one finds, instead of the well known yellowish white 

 ' and very fatty frill-like organ, a frothy thin band without any fat and 

 'and having few folds, often as transparent as glass, otherwise of the same 

 1 length and breadth as the frill organ, varying of course according to the 

 ' size of the eel. If this band is examined under the microscope, the eggs 

 ' appear transparent, containing but very few grains of yolk, or none at all. 

 1 The band therefore appears an anomalously developed ovarium. The 

 1 outward distinguishing marks of the barren females, which I found of 

 ' all lengths up to 70 cm. (28 inches), are very striking. They show all 

 1 the above-mentioned distinguishing marks of the female intensified. 

 ' Their snout is broader, often especially the point of the lower jaw. 

 * Extraordinarily broad, the dorsal fin generally higher, the eyes decidedly 

 'smaller, in larger specimens astonishingly small, and the colour is 

 ' generally a light almost yellowish-green ; the back of a lighter colour, and 

 1 the belly of a brighter yellow than is the common female eels. In 

 1 Comacchio, this eel is called ' pascuite.' By the term i pascuite,' however, 

 1 the fishermen understand immature normally developed eels, as well as 

 ' the sterile females. The sterile females grow as large as ordinary females, 

 ' but never leave the brackish waters.' According to Comisa,* the barren 

 female may probably, under certain conditions, develop into a normal 

 female. 



Eobin f states that, looking to the strongly marked characters of the 

 male eel, one might be led to say that there are few species of fishes in 

 which the external characters are so distinctive of the male in comparison 

 with the female as in the eel. He found that, with very few exceptions, 

 all the eels described under the varietal name of 'pimpeneau,' or 

 1 pimperneauj from the maritime pools and marshes {glut-eel of English 

 authors), with large prominent eyes, a slender cylindriform body, with 

 the back black, and the pectoral fins a little longer than in the river eels, 

 not exceeding 38 or 40 cm., &c, are males. The largest male eel which 

 he observed measured 45 cm. It is not rare to see in pimpeneaux, 

 alongside females of the same size, the pectoral fins almost twice as long 

 and distinctly wider, the eye almost double in size, the iris a little more 

 blackish, the head a little more swollen in front of the opercular and 

 branchial orifice, and the muzzle less elongated in front of the eyes. A. 

 Pouchet, however, has remarked that the difference of tinge from the pale 

 yellow or pale grayish to the intense green colour of some eels, is in 

 agreement with the slimy, sandy, or other nature of the bottom of the 

 water which they inhabit (Zoologie classique, Paris, 1841). 



* Comisa, 'On the Sex of Eels and on the Sterile Females,' in Zeitschr.f. Fischerei, 

 von Dr Weigelt, 1893, No. 4. 



t Robin, 4 Les Anguilles males comparee aux femelles,' Journal de VAiiaton<ie, 

 etc., 1881. 



