REPRODUCTION AND METAMORPHOSIS OF COMMON EEL. 385 
big eyes under conditions similar to those described for the 
eels of these Roman cloace. From these and similar observa- 
tions it clearly results that all the European eels must be in- 
cluded under-a single species; and this is an important fact 
from another point of view, namely, that it destroys an 
objection which might be raised against my conclusion with 
regard to the development of Anguilla vulgaris from Lepto- 
cephalus brevirostris, namely, the objection that Lepto- 
cephalus brevirostris belongs not to Anguilla vulgaris, 
but to Anguilla kieneri, or to Anguilla bibroni. 
To sum up, Anguilla vulgaris, the common eel, matures 
in the depths of the sea, where it acquires larger eyes than are 
ever observed in individuals which have not yet migrated to 
deep water, with the exception of the eels of the Roman 
cloace. The abysses of the sea are the spawning-places of the 
common eel: its eggs float in the sea water. In developing 
from the egg it undergoes a metamorphosis, that is to say, 
passes through a larval form denominated Leptocephalus 
brevirostris. What length of time this development re- 
quires is very difficult to establish. So far we have only the 
following data:—First, Anguilla vulgaris migrates to the 
sea from the month of October to the month of January ; 
second, the currents, such as those of Messina, throw up, from 
tle abysses of the sea, specimens which, from the commence- 
ment of November to the end of July, are observed to be more 
advanced in development than at other times, but not yet 
arrived at total maturity; third, eggs, which according to 
every probability belong to the common eel, are found in the 
sea from the month of August to that of January inclusive; 
fourth, the Leptocephalus brevirostris abounds from 
February to September. As to the other months, we are in 
some uncertainty, because during them our only natural fisher- 
man, the Orthagoriscus mola, appears very rarely ; fifth, 
I am inclined to believe that the elvers ascending our rivers 
are already one year of age, and I have observed that in an 
aquarium specimens of L. brevirostris can transform them- 
selves into young elvers in one month’s time. 
VOL. 39, PART 3,—NEW SER. DD 
