REPRODUCTION AND METAMORPHOSIS OF COMMON EEL. 373 
mally they can only be observed in the abysses of the sea at a 
depth of at least 500 metres. Fortunately, along a part of the 
coast of Sicily strong currents occur, which must be ascribed 
to the tide, producing very large displacements of the water in 
the narrow Strait of Messina. I shall give further details con- 
cerning these currents in my large memoir. In consequence 
of the strong currents sometimes—I say sometimes because 
there is no regularity, and one may have to wait for.a year with- 
out obtaining any material—not only many deep-sea fishes, but 
also all stages of the development of the Murzenoids are met 
with in the surface-water. To these currents we owe all the 
captures of Murzna helena with ripe eggs, which is in ac- 
cordance with what I had already argued from other facts, 
namely, that the reproduction of the Murznoids takes place at 
great depths of the sea. 
Before I proceed to speak of the common eel, I must pre- 
mise that Dr. Raffaele has described certain pelagic eggs as 
belonging to an undetermined species, putting forward the 
suggestion that these eggs belong to some Murenoid. This 
matter has been investigated by myself, and I have shown that 
the newly hatched larve (called “ pre-larve” by me) derived 
from these eggs have essentially the character of Leptocephali. 
The life history of the Murzenoids, leaving aside for the 
present the common eel, is as follows:—Females can only 
mature in very profound depths of the sea, that is to say, at 
least a depth of 500 metres. This fact I established by find- 
ing well-known deep-sea fishes together with Leptocephali, 
ripe Murzene, and quite ripe eels (see below). The females of 
those species which do not live at this depth must therefore 
migrate to it. The male, however, can mature at a smaller 
depth, and therefore they migrate into the greater depth when 
they are already mature. Fertilisation takes place at great 
depths: the eggs float in the water; nevertheless they remain 
at a great depth in the sea, and only exceptionally, for un- 
‘known reasons, some of them mount to the surface. 
From the egg issues rapidly a pre-larva, which becomes a 
larva (Leptocephalus) with the anus and the urinary opening 
VoL. 39, PART 3.—NEW SER. BB 
