164
ANTON F. BRUUN
Conger. To what extent there is a vertical overlapping is not known,
but Tucker's hypothesis, that each of the genera is represented by one
species only, excludes the possibility that the eastern and western
species might have different preferences aa to temperature when
spawning, hence spawning at different levels. It seems impossible to
understand the case of the two Conger species without assuming the
existence of two well established species. About C. conger we know that
we have at least two well-defined breeding populations, one Meditmranean and one Atlantic (Schmidt, 1911). But nothing indicates tha,t
the Sargasso Sea spawners of C. oceanicus should be the parents of the
leptocephali of C. conger occurring in this area. So here i t seems quite
impossible to agree with Tucker that this situation may well be due to
an eco-phenotypy rather than to genetic effects. But if this is 80,
Syqhobranchus can be no different; never have any experiments
shown shock effects of a magnitude such aa the differences in the numbers of vertebrae in the two species of Sywpiaobranclius, not to spertlr
of the Conger species.
So when A. anguilla-A. rostra& and Leptocephalus euryurw-L.
sirnilis are considered, it seems most logical to consider them as paralIe1
cases in the sense that they also represent pairs of genetically different
populations, and that they may not well be due to a common emphenotypy as Tucker suggests.
x. OTHER SPECIES OF APODES BKEEDINU IN THE SARQASSO SEA
Out of the many thousands of leptocephali collected in the North
Atlantic by Schmidt's efforts, only a few species more than hitherto
mentioned have been examined.
One of them was treated by Schmidt himself in four papers (1912,
1930, 1931 ; Schmidt et al., 1932),; this was the leptocephalus of
Nessoritamphus ingoljianus. '' Nessorhumphus ingolfinus must be one
of the commonest species of the North Atlantic. We have not yet
counted up the total number of larvae of this species from all om
cruises in the Northern Atlantic, but I may mention, that on the
summer cruise of 1920 with M/S Dana I, no fewer than 4103 specimens
were taken (against 5959 of Anguilla mlga9&).
" Nessorhumphus ingoljianus spawns in the Sargasso Sea at the same
period as the Eel, i.e. in spring and early summer, somewhat later h
the east than in the west, and the metamorphosis of the larva takplace especiaIly in the months of August, September, and October."
(Schmidt, 1930, p. 374). For this species Schmidt also identified the
egg, and hatched the larva, and was thus able to make firm connection
ANTON F. BRUUN
Conger. To what extent there is a vertical overlapping is not known,
but Tucker's hypothesis, that each of the genera is represented by one
species only, excludes the possibility that the eastern and western
species might have different preferences aa to temperature when
spawning, hence spawning at different levels. It seems impossible to
understand the case of the two Conger species without assuming the
existence of two well established species. About C. conger we know that
we have at least two well-defined breeding populations, one Meditmranean and one Atlantic (Schmidt, 1911). But nothing indicates tha,t
the Sargasso Sea spawners of C. oceanicus should be the parents of the
leptocephali of C. conger occurring in this area. So here i t seems quite
impossible to agree with Tucker that this situation may well be due to
an eco-phenotypy rather than to genetic effects. But if this is 80,
Syqhobranchus can be no different; never have any experiments
shown shock effects of a magnitude such aa the differences in the numbers of vertebrae in the two species of Sywpiaobranclius, not to spertlr
of the Conger species.
So when A. anguilla-A. rostra& and Leptocephalus euryurw-L.
sirnilis are considered, it seems most logical to consider them as paralIe1
cases in the sense that they also represent pairs of genetically different
populations, and that they may not well be due to a common emphenotypy as Tucker suggests.
x. OTHER SPECIES OF APODES BKEEDINU IN THE SARQASSO SEA
Out of the many thousands of leptocephali collected in the North
Atlantic by Schmidt's efforts, only a few species more than hitherto
mentioned have been examined.
One of them was treated by Schmidt himself in four papers (1912,
1930, 1931 ; Schmidt et al., 1932),; this was the leptocephalus of
Nessoritamphus ingoljianus. '' Nessorhumphus ingolfinus must be one
of the commonest species of the North Atlantic. We have not yet
counted up the total number of larvae of this species from all om
cruises in the Northern Atlantic, but I may mention, that on the
summer cruise of 1920 with M/S Dana I, no fewer than 4103 specimens
were taken (against 5959 of Anguilla mlga9&).
" Nessorhumphus ingoljianus spawns in the Sargasso Sea at the same
period as the Eel, i.e. in spring and early summer, somewhat later h
the east than in the west, and the metamorphosis of the larva takplace especiaIly in the months of August, September, and October."
(Schmidt, 1930, p. 374). For this species Schmidt also identified the
egg, and hatched the larva, and was thus able to make firm connection