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Part III. — Thirteenth Annual Report 



The view of Siebold that the eel, like the lamprey, dies after the repro- 

 ductive act, has been accepted by Jacoby, Cattie, Benecke and others. 

 The ovaries of the migrating eel are very immature, and if the swarms of 

 elvers, which ascend the rivers in May, are produced from the eels which 

 migrated in the preceding autumn, the reproductive organs must arrive 

 at a ripe condition with extraordinary rapidity. It is considered probable 

 that the excessively rapid development of their organs of generation 

 exhaust them to such a degree that they die a physiological death soon 

 after they have spawned. Brown Goode quotes an important statement 

 of Dr Schock, published by him in No. 8 German Ficherei Zeitung, 1878. 

 Dr Schock says, on the authority of Jacoby, that occasionally the sea, in 

 the neighbourhood of the mouths of rivers, has been found covered with 

 dead eels, whose ovaries were empty. *■ *When, where, and by whom the 

 ' observations were made, and who pronounced upon the empty ovaries of 

 1 the dead fish are unfortunately not mentioned. Benecke considered that 

 1 the eel lays its eggs like most other fishes, but that like the lamprey it 

 1 only spawns once, and then dies. All the eggs of the female eel show 

 ' the same degree of maturity, while in the fishes which spawn every year, 

 1 beside the larger eggs which are ready to be deposited, there exist very 

 1 many of much smaller size, which are destined to mature hereafter, and 

 ' to be deposited in other years.' The equality in size of the ova seems to 

 Benecke to indicate that all the eggs ripen simultaneously and are shed at 

 one time • and since no ova would remain to become mature in the follow- 

 ing year, that the eel, being therefore useless for further reproduction, dies. 

 Blanchard f also states that the eel which has quitted fresh water never 

 returns. He appears to be of the opinion that the eels after having mi- 

 grated, remain in the sea. With regard to the conger, Cunningham | drew 

 the conclusion that each conger only breeds once in its life, or, in other 

 words, that every specimen, whether male or female, dies after shedding its 

 milt or roe. He found that the congers kept in confinement at Plymouth 

 ceased to feed when the sexual organs began to mature, and died on 

 becoming ripe. On examining certain ripe females and a ripe male, he 

 noticed that the teeth were nearly all gone, and that the bones of the 

 head were soft and flexible. From a comparison between a ripe and an 

 immature female as regards total weight of body, and weights of ovary 

 and alimentary organs, he found that the ovaries increase very much in 

 size and weight during the fasting period at the expense of the rest of 

 the body, while in the total weight of the fish a great reduction takes 

 place. The strongest evidence in support of his conclusion that the 

 conger dies on shedding its milt or roe, was derived, he thought, from the 

 loss of teeth, and the atrophy of the bones of the head, which occurs 

 during the ripening of the sexual organs. ' A conger after it had shed 

 1 its milt or roe would in all probability be incapable of feeding itself ; 

 1 without teeth it would be unable to hold its prey, and without food it 

 1 could not recover its former condition.' Petersen § also believes that the 

 silver eel, which he considers to be the yellow eel in its ' marriage dress ' 

 (Parungskleid), dies after spawning. Hermes,U however, has stated that, 

 according to his knowledge, there are wanting observations which will 

 give scientific foundation to the statement that the common eel dies 

 after spawning. The same view is held by Giinther, who says that the 



* From ' Notes on the Life-history of the Eel,' by Brown Goode. 



t Blanchard, 1 Etude de l'Anguille, apres son passage de l'eaux douces,' in Comptcs 

 Rendus, t. 109, 1889. 



X Cunningham, ' Reproduction and Development of the Conger,' Journal of the 

 Marine Biological Assoc., New Ser., vol. ii., No. 1, May 1891. 



§ Petersen, ' Das Parungskleid des Aales,' in Mittheilungen des Deutschen Seefischer- 

 eivereins, b. xi., No. 2, Februar 1895. 



H Hermes 'On the Conger,' Bull. U.S. Fish. Comm., vol. i., 1881. 



