SOME ASPECTS O F THE BIOLOGY O F THE CHAETOGNATHS
289
not arise because of the absence of apparent glandular cells. What
specific sensory activities are carried out by the corona ciliata and
whether it serves other purposes too, are, as we have seen, open
questions and difficult t o solve, owing especially t o the habitat of
planktonic chaetognaths and the difficulties t h a t have t o be met in
growing them or at least in keeping them in suitable experimental
conditions for a long enough time to carry out significant experiments.
111. REPROUUCTJON
There are not many works of a morphological character on tho
gonads and the biology of reproduction in chaetognaths, i.e. works
dealing with the deposition of eggs and their ripening, and with peculiar
cariologic and cytological problems, as for instance the question of the
germ cells determinant and the origin of the germ line. I n historical
sequence, the following works may be quoted : Butschli (1873), Hertwig
(1880), Grassi (1881, 1583), Bolles-Lee (1888), Doncaster (1902),
Stevens (1903, 1905, 1910), Elpatiewsky (1909, 1910, 1913, 1914),
Buchner (1910a,b), Bord&s (1912, 1914, 1920), Kramp (1917), Huntsman and Reid (1921), Vasiljev (1925), Burfield (1927), Tuzet (1931),
Russell (1932a,b), John ji933, 1943), Sanzo (1937), Kuhl (1938), Kuhl
and Kuhl (1965), Ussing (1938), Jagersten (1940)~ Dunbar (1941, 1962),
Thomson (1947), Pierce (1951), Tchindonova (1955), David (1955,
1958a,b, 1965), Furnestin (1958), Colman (1959), Murakanii (1959),
Hirota (1959, 1961), Elian (1960), Owre (1960), Ghirardelli and
Brandi (1961), Alvariiio (1965), Ghirardelli and Arnaud (1966), Dallot
(1966), MacLaren (1966), Stone (1966) and Ghirardelli (1951, 1953a,c,d,e,
1954a,b,c,d, 1955, 1956a,b, 1959b,c,d, 1960, 1961a,b,c, 1962, 1963a,c,
1966a,b).
Some of these, like Grassi’s large monographs, have already become
classics, but notwithstanding their great value they must be considered
cs obsdeto in some respects ; other works like those by Stevens make a
useful contribution. A larger number of them, however, are confined
to some particular problem, which often, as we shall see later, appears
t o be far from solution. On the other hand, the researches which are
being carried out for ecological purposes in all the seas of the world on
the distribution of these organisms, and also on the periods of their
sexual maturity, may certainly profit from a deeper knowledge of
the morphological and biological facts concerning their reproduction.
A. The malP genital apparatus
The chaetogmths are hermaphrodite ; the male gonads are in the
tail section, while the female ones are in the posterior part of the trunk,
289
not arise because of the absence of apparent glandular cells. What
specific sensory activities are carried out by the corona ciliata and
whether it serves other purposes too, are, as we have seen, open
questions and difficult t o solve, owing especially t o the habitat of
planktonic chaetognaths and the difficulties t h a t have t o be met in
growing them or at least in keeping them in suitable experimental
conditions for a long enough time to carry out significant experiments.
111. REPROUUCTJON
There are not many works of a morphological character on tho
gonads and the biology of reproduction in chaetognaths, i.e. works
dealing with the deposition of eggs and their ripening, and with peculiar
cariologic and cytological problems, as for instance the question of the
germ cells determinant and the origin of the germ line. I n historical
sequence, the following works may be quoted : Butschli (1873), Hertwig
(1880), Grassi (1881, 1583), Bolles-Lee (1888), Doncaster (1902),
Stevens (1903, 1905, 1910), Elpatiewsky (1909, 1910, 1913, 1914),
Buchner (1910a,b), Bord&s (1912, 1914, 1920), Kramp (1917), Huntsman and Reid (1921), Vasiljev (1925), Burfield (1927), Tuzet (1931),
Russell (1932a,b), John ji933, 1943), Sanzo (1937), Kuhl (1938), Kuhl
and Kuhl (1965), Ussing (1938), Jagersten (1940)~ Dunbar (1941, 1962),
Thomson (1947), Pierce (1951), Tchindonova (1955), David (1955,
1958a,b, 1965), Furnestin (1958), Colman (1959), Murakanii (1959),
Hirota (1959, 1961), Elian (1960), Owre (1960), Ghirardelli and
Brandi (1961), Alvariiio (1965), Ghirardelli and Arnaud (1966), Dallot
(1966), MacLaren (1966), Stone (1966) and Ghirardelli (1951, 1953a,c,d,e,
1954a,b,c,d, 1955, 1956a,b, 1959b,c,d, 1960, 1961a,b,c, 1962, 1963a,c,
1966a,b).
Some of these, like Grassi’s large monographs, have already become
classics, but notwithstanding their great value they must be considered
cs obsdeto in some respects ; other works like those by Stevens make a
useful contribution. A larger number of them, however, are confined
to some particular problem, which often, as we shall see later, appears
t o be far from solution. On the other hand, the researches which are
being carried out for ecological purposes in all the seas of the world on
the distribution of these organisms, and also on the periods of their
sexual maturity, may certainly profit from a deeper knowledge of
the morphological and biological facts concerning their reproduction.
A. The malP genital apparatus
The chaetogmths are hermaphrodite ; the male gonads are in the
tail section, while the female ones are in the posterior part of the trunk,