274 On the Generation and other obscure Fads 



and only in ihe darkest and most tenipesluous nights* 

 lyioonshine wlioHy suspends ihuir progress; and even a tem- 

 porary gleam of iiglit, when the nigiil is otherwise favour- 

 able, immediately interrupts their journey. This proves 

 that their cniigration is not a casual but a premeditated 

 system in their existence : and it also displays iheir inslmc- 

 tive cunning; for, being an easy prey, when discovered, to 

 otters, herons, and other nocturnal enemies, it is only in 

 the darkest nights that they can travel in safety." During 

 the period of their run, vast quantities are caught in bag- 

 nets set across the, streams. There is reason to suspect that 

 all the eels in rivers do not run for the sea, as very early 

 in the spring large e-els abound in rivers at such a'distance 

 in-^and, as renders it highly improbable that they can have 

 ascended so far at so early a period; and inuc-cd it is yet an 

 unascertained fact, whether, of the vast multitude which 

 unquestionibly do pass downwards to the sea, any of them 

 do again return and ascend to any distance up the streams. 

 If, indeed, this retrograde emigration really existed to any 

 extent, there are thousands of situations on oui- streams 

 where it must have been every season perceived ; and yet it 

 has not only not been discovered, but the instances are fre- 

 quent, where the obstacles on many of our streams render it 

 impracticable, and where, nevertheless, large eels are found 

 above these obstacles as early and as abundantly as below 

 them. The probability therefore is, that few or none of the 

 vast numbers which descend the streams ever again return; 

 and then, as they are never discovered in the sea itself, the 

 question of what ultimately becomes'of them, is just as 

 obscure as that of their generation. 



There are many lakes, and multiiudes of pools, abound- 

 ing with eels, and Irom which they cannot run on account 

 of the insufliciency of the outlets ; and in these situations 

 the eels most certainly continue during the period of their 

 existence. There, however, ithey regularly disappear, in 

 winter, and the manner of theii: hibernating is entirely un- 

 known ; but as no species of animal with which we are ac- 

 quainted ever does breed during the tinie of its hiberna- 

 tion, (the thing indeed seeming physically impossible,) and 

 as eels in these confined situations are taken at all other 

 times, without any vestige of propagation being dis- 

 covered amongst them, the inference seems conclusive, 

 that eels never do. under any circumstance, breed in fresh 

 water. Were it indeed practicable in a single instance, it 

 would be equally so in thousands of others where the cir- 

 cumstances arc so similar; and it would be passing strange 



if 



