202 Fart III. — Thirteenth Annual Report 



! 400 min. (16 inches) and more, whose genital orifice and deferent canal 

 1 were invariably open, while in some of the smaller ones they were closed, 

 ' and in others open.' Ryder examined a series of male eels obtained from 

 Wood's Hull, Mass., in November 1881, which showed the Syrskian 

 organ slightly larger than that found in certain Fire Island specimens, 

 captured near the shore in September. ' This fact indicates possibly that 

 ' functional maturity of the male organ is not attained till midwinter. 

 ' The eels in both instances showed the male reproductive organ so far 

 ' advanced that there can be but little doubt, if the animal had been taken 



■ a few weeks later, ripe spermatozoa would have been found in the vasa 



■ deferentia of the testis.' 



The Male Eel. 



The male eel has not been known to exceed 480 mm. (19| inches) in 

 length. A male eel of this size was found by Jacoby at Comacchio. 

 The smallest male recorded measured 240 mm. (9| inches), and was pro- 

 cured by Jacoby in the same locality. 



The question as to whether or not the male eel enters fresh water has 

 given rise to much difference of opinion. It was generally believed that 

 the male eel never left the brackish or salt water near the coast, except at 

 the period of reproduction, when it joined the females which had migrated 

 from the fresh water streams. This view has now been modified. The 

 observations of Hermes, Pauly and Feddersen have proved that males do 

 go up the rivers into the fresh water. In 1880 male eels were procured 

 by Dr Hermes at Cumlosen on the Elbe, 120 miles from the German 

 Ocean. The following account of the observations of Dr Pauly is taken 

 from the article on <( The Life-history of the Eel," &c, by Brown Goode, 

 in the Bull. U. S. Fish. Commission, vol. i., 1881 : — A theory had been 

 propounded by some one, that eels are at first of undifferentiated sex, and 

 have the tendency under the influence of fresh water to become females, 

 under that of salt water to develop male characters. It has however been 

 shown by Pauly that among the very young eels (montee) taken near the 

 mouths of rivers, there is a considerable percentage of males which, when 

 transplanted to fresh water, will there retain their masculine characters 

 and develop into perfect adult males. Pauly received from Kuffer a lot 

 of eels weighing from 20-90 gms. (f-3 oz.) each, taken in fresh water. 

 A large majority, 19 out of 27 of these small eels, were found to be males. 

 Kuffer had received them two years previously from a French river, the 

 Sevre niortaise, where they were caught as young fry (montee) at a dis- 

 tance of 10 or 12 miles from its mouth, and furthermore, were at the 

 time of their examination four years old. The females in this lot of eels 

 exceeded the males in length and weight, and also exhibited the external 

 characteristics described by Jacoby as indicating sex. The locality of the 

 Sevre niortaise, where the fish were taken, may easily, especially at flood 

 tide, have been within the limits of brackish water. Pauly claims that 

 his investigations and those of Jacoby prove that the young female eels do 

 not necessarily break away from their parents and their birthplaces at 

 sea, and alone proceed on their migration, while the males scatter through 

 the sea, but that their brothers seem to accompany them part of the way 

 upon their journey. He maintains that male eels undoubtedly ascend 

 the rivers, but the numerical percentage of males to females appears to 

 diminish as one proceeds up the stream. 



Finally, Feddersen * arrives at the conclusion— 



* Feddersen, Dcvnsk Fiakeri-forenings Medlemsblad, No. 35, Aug. 1893. 



