: 
26 The Breeding Habits of the Eel. [January, — 
Mooney, were distinguishable by the naked eye, were well filled 
with yolk cells, with a clear nucleus, and measured nearly two 
millimetres (1.90 inch) in diameter. The under side of the eel 
was tinged with golden-yellow. Mr. Mooney’s so-called male — 
was darker, dull silvery beneath. A microscopic examination 
showed that the thin sexual gland was quite different in histologi- 
cal structure from that of the ovary, and the examination of sev- 
eral undoubted male eels, with active spermatozoa, showed that 
Mr. Mooney was right in his conjecture that his supposed male 
was really such. 
Fourteen eels were then obtained, from twelve to about sixteen | 
inches in length, and ten of them were examined with a Tolles 
fifth and Hartnack immersion, No. 10. Several females were 
- examined, and it was found that it was easy with the microscope 
to determine the sexes, from the different nature of the histologi- 
cal structure of the reproductive glands. The results of our 
examination are as follows: The males are abundant, and it — 
seems probable that there is an equality in the number of indi- — 
viduals of the sexes. When about a foot in length, namely, 
when the eels are about a year old, there are no external structural 
differences, but at this period the males contain sperm i 
sperm cells and immature (?) spermatozoa. 
When the eels are from eighteen inches to two feet in length, 
in the autumn and early winter, the external sexual characters — 
appear. This is confined to the style of coloration. No external 
structural characters could be detected, the form of the head, lips, 
body, fins and even the single genital pore being identical in the © 
two sexes. In color the females are of a rich yellow on the 
under side, especially the long anal fin; the median line is silvery, — 
but on each side there is a pale yellowish line. In the males the — 
yellowish tint is entirely wanting, except on the long anal fin, the l 
belly is dull silvery, and pigment spots are numerous heneath the — 
head. 
It is probable that the females are larger than the males, and 
when the ovaries are filled with ripe eggs, the body is a little n 
-more swollen than in the males. 
The testis, as well as the ovary, is in the eel attached by © 
one edge to each side of the intestine, and hangs vertically — 
down i in the body cavity. There is no oviduct, but the eggs or 
er particles, as the case may be, drop directly by s 
easa h nas 
