48 
For the generation of Hels it would seem, so far as we at 
present are aware, that the presence of salt water is a necessity, 
for it has been observed that when these fish leave rivers and 
brackish waters for the sea, their reproductive organs have 
scarcely begun to develop. But their maturing in the sea must 
be rapid, because in five or six weeks they have arrived at a 
breeding condition. This rapidity of maturing in the breeding 
organs would seem to be a cause of extreme exhaustion. 
Consequently, after the breeding season is over they die, simi- 
larly to lampreys and several other piscine forms; and this 
furnishes the explanation why subsequent to this period old 
Eels are not observed re-ascending rivers. 
The appearance of the generative organs in Hels at the 
breeding season may be shortly described as follows :—On 
opening a female, besides the liver, intestinal canal, and’ an 
elongated air bladder, which is pointed at both ends, one sees 
on either side a white or yellowish band extending from the 
liver backwards, as far as the vent. This band is rather 
broad, and shaped like a frill, while its inner edge is attached 
by a narrow slip of membrane to the air bladder. These 
frill-like bands contain a large amount of fat, in which. . 
numerous eggs may be found to be embedded. Should a piece 
be torn off with a pin, and the drops of fat carefully removed 
by wiping, the ova may be seen in the form of small white 
dots, and, placed under the microscope, all doubts as to what 
they are will be at once solved. But large eggs, or those on 
the point of becoming detached from the ovary, in order to be 
deposited, fecundated, and subsequently hatched into young 
Eels, have yet to be discovered, and such will probably only be 
found in fish captured at some distance out at sea, or else in 
such as have been detained in an aquarium. 
The generative organs of the male Kel, as I have already 
remarked, show no frill-like bands, but the observer must not 
Eels which migrate tothe sea appear to return to fresh water, but not ina 
body, but irregularly, and throughout the warmer part ,of the year,” (page 
672.) Buckianp having remarked that it is disputed whether the parent 
Fels ever return into rivers, continued ‘‘my own opinion is that they do so,” 
and the “ up-parent Eels,” he fancied, went singly. 
