REPRODUCTION AND METAMORPHOSIS OF COMMON EEL. 381 
out acquiring well-developed teeth, and without nourishing 
itself. 
In conclusion, no one would hesitate, even not knowing 
Leptocephalus brevirostris, to refer the stage now under 
discussion to a Murenoid about to complete its Leptocephalus 
metamorphosis, were it not for the fact that there has been so 
much question concerning the reproduction of the common 
eel, and that so many capable observers have failed in dealing 
with it, that every new observation is received with scepticism. 
The stage of which I am now speaking, in the hands of a 
pure systematist, would probably be described as a Helmichthys, 
a genus established for certain forms of Leptocephali far 
advanced in transformation. 
The next forms to which I have to refer are captured in the 
course of migration from the sea into fresh water. When kept 
in an aquarium they assume the characters of the elver, dimin- 
ishing more or less in volume, and without nourishing them- 
selves. The elvers of the common eel can present themselves 
in stages differing little from that last described, as well as in 
a form which has already developed the full pigmentation of 
the adult. Even those which most resemble the preceding 
stage always have a character which distinguishes them easily, 
namely, the presence of a definitive pigment, more or less 
superficially placed on the head, and not to be confounded 
with the pigment round the posterior extremity of the brain, 
which latter is already present in the preceding stage. In 
specimens taken at the mouths of rivers this more or less 
superficial pigment was, so far as I could ascertain, always 
present. 
As the pigmentation develops itself, the little eel gradually 
undergoes a diminution in all its dimensions. It results from 
my measurements, that the fully pigmented elver has an 
average length of 61 mm., while for the more or less colourless 
elver the average length is 67 mm. I found pigmented elvers 
which were reduced in length to 51 mm.,a size which I never 
observed in those elvers in which the development of pig- 
ment had not taken place. 
VoL. 39, PART 3,—NEW SER. cc 
