REPRODUCTION AND METAMORPHOSIS OF COMMON EEL. 375 
enough, however, to allow us to observe that it is their habit 
to conceal themselves in the sand or in the mud as the common 
eel (Anguilla) does. Here it is to be noted that the various 
forms of Leptocephali have habits resembling those of the 
Murenoids to which they belong, i.e. they dig into the sand 
or abstain from doing so according as the adult form has or has 
not this habit. 
I now pass on to the characters of Leptocephalus brevi- 
rostris. I give them here in the same order as I shall use in 
my larger memoir. The length varies from 77 to 60 mm., the 
same extent of variation as observed in other Murenoids. 
The caudal fin tends to assume the form which it has in the 
Elver! or young Anguilla. It is to be noted that in other 
Leptocephali the caudal fin also tends always to exhibit the 
adult form. The lower jaw projects sometimes more than the 
upper jaw, asin Anguilla. The margin of the mouth is wide, 
as in Anguilla. The tongue is free, as in Anguilla. On the 
other hand, the youngest elvers which I have observed have 
smaller eyes than Leptocephalus brevirostris, and this 
need not surprise us, since we know that in other species of 
Murenoids the diminution of the eyes occurs during the 
metamorphosis. The nostrils are separated from one another, 
the anterior tubes are relatively at a considerable distance from 
the tip of the snout and from the rim of the mouth. They 
are in a position in which they are observed in many other 
Leptocephali, which are destined to transform themselves into 
adult forms having the anterior nostrils in nearly the same 
position as in the commoneel. The posterior nostrils, on the 
contrary, are not tube-like, and are in the same position as 
those occupied in the adult Anguilla. It is worth remarking 
that in other Leptocephali also the posterior nostrils have 
already assumed the adult position when the anterior ones are 
still far removed from it. In L. brevirostris I find a larval 
dentition which resembles that of the other Leptoce- 
1 The word “ Elver” is used in this paper in its strict sense, viz. for the 
young form of Anguilla vulgaris as taken when ascending rivers in vast 
numbers. 
