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Part III. — Thirteenth Annual Report 



from one piece of water to another, is a well-known fact. The presence 

 of eels in ponds, into which they have not been introduced, and which 

 are isolated from all other waters, can only he accounted for by the passage 

 of the eels over land from some stream connected with the sea. Some 

 persons have asserted that eels crawl over fields in search of slugs, etc. 

 ' The adult eel,' says Jourdain,* f will travel over wet grass to ponds or 

 1 water-courses which have no direct communication with the sea. Out 

 4 of water, the eel swallows air into its branchial chamber, the straight 

 1 opercular opening of which closes very exactly. The gill is then in a 

 ' humid chamber, where the air gives up a portion of its oxygen to the 

 ' branchial lamellae, which can be partly separated from one another by 

 ' the play of the muscles of the respiratory apparatus. This is one of the 

 ' conditions which favour the long survival of the fish out of the water.' 



Problems remaining to be Solved. 



1 No one,' Comisa remarks, has yet observed — 



(1) . The development of the young eel from the egg. 



(2) . That the so-called syrski's organ contains spermatozoa. 



(3) . That eels whether male or female, that have migrated to the sea 

 ever return. 



(4) . Eels in the sea that have spawned. 



And to the above there may be added, the problem — 



(5) . The determination of the life of the eel in the sea, and the place 

 and manner of the extrusion of the ova. 



Jacoby asks, ' why, at some distance, one to two nautical miles from 

 ' the coast, none of the many thousands of grown eels which have migrated 

 ' to the sea are seen ? [One female has been obtained by Calderwood, vide 

 1 above]. This phenomenon is explained,' he says, ' when one thinks of 

 1 the methods of fishing, and the nets employed by the sea fishermen. The 

 1 nets, which, like those employed in the lobster fisheries, are intended to 

 ' be dragged along the bottom of the sea, have very wide meshes, much too 

 ' wide to retain an eel which can slip through a very small hole. And 

 ' those nets which have narrow meshes never reach the bottom of the sea ; 



* the eels, however, can only be brought up from the bottom of the sea. 

 ' The drag nets, w r hich the fishermen employ, are, moreover, deficient in 

 ' this respect that they do not have an apparatus to dig up the sand which 

 ' is the favourite habitation of the eel, but glide over it gently. To catch 

 1 a river eel in the open sea, which is an essential condition of solving the 

 ' most perplexing question of the eel problem, will, therefore remain an 

 ' impossibility so long as we do not possess vessels, and apparatus specially 

 1 adapted to this purpose.' 'It is only,' writes Robin, 'in the common 

 1 eels taken at sea from November to February that it will be necessary to 

 1 seek spermatozoids and ova. I have ascertained that in October there 

 1 are as yet no fecundating elements, and that in January there are no 

 \ longer any.' 



Brown Goode, in this connection, says, 1 The eel eggs can only be found 

 1 by the systematic investigation of the sea-bottom with the dredge 

 1 and microscope. The investigation might also include the sinking of 

 1 the migrating eel, in special boxes, to the bottom of the sea, in order to 



• determine whether under these circumstances the eggs would ripen 

 ' more rapidly. By using the largest eels for this purpose we could 

 ' arrange, by means of small openings in the cases, to permit the entrance 

 1 of the small male eels.' This experiment was tried by Mobius, who 

 placed twenty-three female and three male eels in a box which was kept 



* Jouvdain. Loc. cit. 



