112 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



sea, not close to the shore, but at a distance and in deep waters. This 

 development is extraordinarly raj)id when the immature state, in which 

 the migrating eels are found, is taken into consideration ; they must 

 become sexually mature within a few, probably five or six, weeks of the 

 time that they enter the sea. At Comacchio the emigration takes place 

 between the beginning of October and the end of December. 



Question 3. Where does the act of spawning take place, the fertiliza- 

 tion, and the deposition of the eggs ? 



Answer. There are probably certain definite spawning jilaces in the 

 sea, off the mouths of the rivers. These are the mud-banks to which the 

 eels go, for the ijurpose of spawning, in great numbers. The young fish 

 are developed upon these mud-banks, and from eight to ten weeks after 

 their birth, at the beginning of spring, find their way to the mouths of 

 rivers, which they ascend. 



Question 4. What becomes of the grown-up eels after spawning time, 

 and why do they remain lost to sight and never again come back into 

 the rivers'? 



Answer. The old eels, male and female, without doubt, die soon after 

 the spawning season. The very unusual rapid development of their re- 

 productive organs has such an effect upon the systems of the adult eels 

 that they die soon after the act of reproduction. This is the reason why 

 they are never seen to wander back again.* 



An intelligent Chioggian, the owner of a fishing vessel, in answer to 

 my question, as to where the old eels staid, answered, "They die on the 

 mud-banks after they have propagated their young." 



This hypothesis may be confirmed in a scientific manner by the anal- 

 ogous circumstances in the history of the lamprey. Panizza, in his 

 description of the sea lamprey, Petromyzon marina, remarks', that both 

 the males and females of this species after the spawning " period are 

 brought up dead. Concerning the river lamprey, P. fluviatilis, Statins 

 Miiller remarks that when they spawn they slowly fall away and die. 

 Concerning the little lamprey, P. planeri, August Miiller, the discoverer 

 of its larval form, has recorded the same opinion. 



XX. — A LIST OF THE MOST IMPORTANT PAPERS CONCERNING THE 



EEL AND ITS REPRODUCTION. 



1684. Eedi, Francisco. Osservazioni intorno agli animali viventi che 



se trovano negii animali viventi. Florence, 1684. 



["Ou living animals wMcli occur witliiu other animals." Refers to the 

 mountiuj^ of the young eels in the Aruo, and particularly to an enormous cap- 

 ture of young eels at Pisa, in 1667, [p. 100]. Illustrates the ovaries of a maray 

 (Murcena lielena). Proves that the objects ordinarily supposed to be young 

 eels are intestinal vrorms, and argues that eels must be viviparous. ] 



* As a confirmation of this view, Von Siebold was the first to make this hypothesis. 



