BULLETIN OF THE UNITED STATES FISH COMMISSION. 99 



examination of these orjjans convinced me that the structure of these 



tissues agreed with that described by Freud. 



******* 



My next inquiry was very naturally concerning the locality whence 

 these eels had been obtained. I learned that Kuffer had received them two 

 yeai'S before from Director Haack at Hiiningen, and upon questioning 

 Director Haack learned that they had been brought from a French 

 river, the sevre niortaise, where they were caught as young fry [montee] 

 at a distance of ten or twelve miles from its mouth, and furthermore 

 were at the time of examination about four years old. The small size 

 of these fish, their age being taken into consideration, satisfied me that 

 they had been reared in captivity, since uncultivated eels would have 

 been much heavier. The females in this lot of eels exceeded the males 

 in length and weight and also exhibited those external characters de- 

 scribed by Jacoby as indicating sex. 



The locality in the sevre niortaise where these fish were taken may 

 easily, especiallj^ at flood tide, have been within the limits of brackish 

 water ; my observations do not prove, therefore, that male eels enter 

 fresh water. 



Dr. Jacoby found male eels in the lagoons of Comacchio, where the 

 water is brackish. These males must have ascended in the "mountmg" 

 as fry, and probably at the approach of sexual maturity descend with 

 the females to the sea. My investigations and those of Jacoby prove 

 only this : that the young female eels do not necessarily break away 

 from their j)arents and from their birth-places at sea, and entirely alone 

 proceed upon their migrations, while the males scatter through the sea, 

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

 their journey. But how far? Do the males know where pure fresh 

 water begins, and are the fry of different sexes found mingled together 

 only at the river mouths? If we bear in mind the fact that the male 

 organs had so long escaped discovery, that, on account of their crystal- 

 like transparency, their detection in a fresh eel is so difficult, etc., may 

 we not admit that past conclusions are probably erroneous, and that 

 although thousands of fresh-water eels have been studied by different 

 investigators, male eels may yet be found in our streams, especially 



when more of the smaller individuals have been examined." 



**** **** ** 



Dr. Pauly then discusses the observations of Dr. Hermes, who found 

 11 per cent, of males among eels taken at Willenberg, on the Elbe, about 

 120 miles from the German Ocean, and no males whatever atHavelberg, 

 20 or 30 miles higher up the stream, and closes his essay with the fol- 

 lowing conclusions : " 21ale eels iindouhtedly ascend the rivers^ hut the 

 numerical percentage of males to females appears to diminish as one pro- 

 ceeds up the streams.''^ This fact is opposed to the theory i)roposed by 

 some one that young 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." 



