[11] THE EEL QUESTION. 473 



shows a beautiful aud regularly wavy outline. By these convex inden- 

 tations the whole band is regularly divided into small pieces, or little 

 lobes, from which the organ, in contradistinction to the frill-organ of the 

 ovarium, is called the lobe-organ (" Lappen-organ "). This organ, which 

 in such perfection is not found in any other fish, is now generally called, 

 from its discoverer, the Syrski organ. The inner structure and histo- 

 logical construction of this organ is also very different from that of the 

 ovarium. Whilst the contents of the latter, even when only moderately 

 magnified, appear beyond a doubt as eggs imbedded in layers of fat, 

 the elementary structure of the lobe-organ can only be recognized when 

 strongly magnified. Under a powerful microscope no ovarian cells can 

 be seen, but a net-work resembling closely the histological structure 

 of the immature testicles of other fish. Professor Claus, of Vienna, who 

 like other German scientists, for instance, Professor Siebold, of Munich, 

 and Professor Virchow, of Berlin, takes a very lively interest in this 

 question, had one of his scholars, Mr. S. Freud, a student of medi- 

 cine, examine histologically the lobe- organ of a large number of eels. 

 Although this observer could not pass a definite opinion, because he 

 was not able to prove the presence of spermatozoids, he likewise draws 

 attention to the great difference between the ovarium and the lobe- 

 organ, and to the probability that the latter is the testicle.* When 

 engaged at the zoological station at Trieste, I devoted considerable time 

 to an examination of this question. In September, 1877, I obtained an 

 eel which had unusually large lobes, and which, at the special desire of 

 Professor Claus, was sent to Professor Siebold, of Munich, for examina- 

 tion by the naturalists then in convention in that city. I had succeeded 

 in showing in this eel a more advanced stage of development of the 

 inner construction, namely, tube-like ducts filled with cells, exhibiting an 

 unmistakable resemblance to the seminal cells of the testicles of other 

 fish. 



It is interesting to observe the outward difference between live eels 

 having an ovarium and those having a lobe-organ. The most impor- 

 tant difference is (1) that of length and size, already referred to. Syrski 

 says that the largest eels with lobe-organs discovered by him measured 

 430 millimeters. I have, however, both at Trieste and Comacchio, found 

 eels with this organ measuring 450, 460, 470, and 480 millimeters. All 

 eels longer than this — and it is well known that they reach the length 

 of one meter, and the thickness of a man's arm — have so far at least been 

 invariably found to be females. The other outward differences are (2), 

 the broader point of the snout in the female in contradistinction to 

 the narrow, extended, or short and pointed snout of the eel with lobe- 



by carefully turning over and laying back the fatty folds. The lobe-sbaped band fas- 

 tened to the backbone is, however, often so narrow, and its substance is so glass-like 

 and transparent, that this organ when attached to its base can only be recognized 

 with the naked eye when it is held in an oblique direction towards the sun. 



* Published in the March number of the " Sitzungsberichte der K. Academie der 

 Wissenschaften zu Wien." 1877. 



