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population. Basing his belief on the established fact that larval tuna
are unknown in the zones of the fisheries, he supposes that the larvae
are negatively phototropic and that they go very deep to the lower strata.

It is a fact that even the Thor succeeded in its cruises in
capturing only a very limited number (13) of juvenile stages^ which
Ehrenbaum (Danish Ocean. Exp., vol. II, 1924), who described this
material, attributed only doubtfully to the tuna (and in truth, in Ariew
of material in my possession which I have already described in part
elsewhere, see Rend. R. Acco Lincei, 1924, I do not believe that they
are tuna)o

As a matter of fact we have taken in the Strait of Messina
repeatedly, in different years, thousands and thousands of larval tuna
on the surface with lightsli/ and in the cruise of the Ciclope in June
of 1913 along the north and east coasts of Sicily we took with plankton
nets several dozen juvenile stages of tuna at different depths.
As for the tuna's being negatively phototropic, I mast record the
fact that the catches mentioned above, made in the Strait of Messina,
have demonstrated that the juvenile stages of the tuna react violently,
in a^ positive sense , to artificial light to such an extent that they
have been taken with a simple dipnet under the light. This instinct is
later modified gradually and profoundly with age . Tuna barely past the
larval stage move very swiftly and therefore a special skill is necessary
for their capture. In any case the short period of incubation of the
tuna's eggs, and the rapidity with which the larvae and the juvenile
forms not only grow but also acquire independence of movement certainly
preclude the possibility of the occurrence of a passive movement of tuna
from the major centers of reproduction of the Mediterranean (Sardinia,
Sicily, Tunisia, and Tripolitania) to the Atlantic At the age of 15
days the tuna may already be considered an active fish^

The situation is different in the zone adjacent to the Strait of
Gibraltar, where on the Atlantic side we have a very important spawning
area, while on the Mediterranean side there are no reports of any such,
or at least there are no tuna fisheries. De Bu'^^n has already pointed
out the possibility of the passage of eggs and larvae, emphasizing that
iti the region just this side of the Strait, between Ceuta and Melilla,
great quantities of juvenile tuna are collected; I note, however, that
the tuna of which he speaks are already fish of some size, from several
hundred grams to several kilograms, that is, perfectly active and even
capable of having migrated spontaneously. Tuna hatched in June already
weigh 300-500 grams in September and are already taken on trolling lines.

w These collections were ipade for me by Prof. Sanzo, to whom I

am indebted for much assistance in these researcheso