98 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



(6.) In 1879, at Trieste, by Dr. Hermes, who fouud 15 males among 20 



eels selected by Dr. Syrski. 

 (7.) lu 1880, on the Baltic coasts of Denmark, by Dr. Hermes. Out of 

 one lot of 30 from Wismar, he obtained" 8 males, thus repeating 

 Van Siebold's observation. 

 (8.) In 1880, from the Baltic between Zealand and Saland, Denmark. 



Out of one lot of 30, Dr. Hermes obtained 8 males. 

 (9.) In 1880, in France, by Eobin. 

 (10.) In 1880, by Cattie. 

 (11.) In 1880, hy Dr. Hermes, at Cumlosen, on the Elbe, about 120 miles 



fi-om the German Ocean. 

 (12.) In 1880, at Rligers on the Baltic, by Dr. Hermes, who found 44J 



per cent, males in one lot of 137. 

 (13.) By Dr. Pauly, among eels planted at Hiinnigen, in Elsass.-Loth- 

 ringen. See below. 



It has been shown by Dr. Pauly that among the very young eels 

 [montee] taken near the mouths of rivers is a considerable percentage 

 of males, which, when transplanted to fresh water, will there retain 

 their masculine characters and develop into perfect adult males. This 

 discovery is, of course, of the utmost importance to fish culturists mak- 

 ing the attempt to introduce eels into new waters. Its imi3ortance has 

 already been pointed out by Director Haack. 



The practical lesson to be learned is simply this — that young eels, for 

 introduction into strange waters, must be taken from very near the 

 mouths of rivers, in order that both males and females may be secured. 

 The interest to zoologists lies in the fact that Pauly's discovery renders 

 the theory of Van Siebold less plausible, indicating that the sexes 

 of the young eels are differentiated before they begin to mount the 

 rivers and that the males do not ascend beyond the limits of brackish 

 water. 



Dr. Pauly's discovery is so interesting that I propose to translate his 

 own account of it. The investigation was made, I believe, in Munich, 

 and the report from which I quote was published in the Austro-Hun- 

 gariau Fishery Gazette, of Vienna, December 23, 1880. Dr. Pauly 

 writes : " During the past year I have received from Court-fisherman 

 Kuflfer a large number of eels, which I have used in my investigations. 

 The large individuals, all of which came from the lakes of northern 

 Italy, were females. I received, however, from the same individual, 

 another lot of eels, consisting of much smaller individuals, weighing 

 from 20 to 90 grams (f of an ounce to 3 ounces), also taken in fresh 

 water. At the request of Professor Von Siebokl, I had paid particular 

 attention to the sexes of the eels which I was engaged in investigating, 

 and to my great astonishment I found that a large majority of these 

 small eels (19 out of 27) were males, possessing, instead of the familiar 

 ovaries, the "lapiienorgan" described by Dr. Syrski. A histological 



