D E V E L O P M E N T S IN SEXUAL O R G A N O G E N E S I S
261
1960); Gallien (1965); Hartmann (1956); Burns (1955b, 1961); Russell
(1961); Bacci (1965); as well as comprehensive collections of reports: Sex
and Internal Secretions (Allen, 1934, 1939; Young, 1961); Colloques Internationaux du C.N.R.S. (1950); Intersexuality (Overzier, 1963); Intersexuality in Vertebrates (Armstrong and Marshall, 1964); Organogenesis
(De Haan and Ursprung, 1965).
II. Epigenetic Controls during Sexual Differentiation in the Invertebrates
The most significant recent work has been carried out on hydras (Coelenterata), insects, and crustaceans.
A. Sexual Differentiation in Hydras: Intersexuality
and Experimental Sex Reversal
Owing to the simplicity of their structure, the hydras have made possible
an experimental analysis of the essential aspects of the factors involved in
sexuality: relationship between blastogenesis and gametogenesis, origin of
germ cells, beginning of gametogenesis, and the sexual orientation of the
germ cells toward spermatozoa or oocytes (Brien, 1961, 1962a,b, 1963;
Brien and Reniers-Decoen, 1949, 1950, 1951, 1955).
For the hydras as a whole, genetic determination is considered to be
relatively labile. Although Hydra fusca is strictly gonochoric, H. attenuata,
which is normally gonochoric, has, by accident, an intersexual phase,
characterized in the female by the temporary development of testicular
structures in a specific region. In H. viridis, which is hermaphroditic, the
upper part of the body column develops testicular swellings, below which
are ovaries, while the base of the column develops buds under suitable
physiologic conditions (Fig. 1). This aspect of specific regions related to
sexuality must be emphasized. In addition the region under the hypostome
contains a supply of the interstitial cells that give origin to gametoblastic
and somatoblastic cells. Among the latter the cnidoblasts that give rise to
nematocysts are particularly interesting with respect to their cellular
differentiation.
Sexual function is linked to a very simple structure. The gametes differentiate from interstitial cells in swellings that rupture to liberate the
genital products. There is no reproductive tract. The development of the
egg is external.
The hydra is renewed constantly by wearing away of the pedal disc, and
the cells forming in the region of the hypostome proliferate and spread out
in the direction of the disc. These facts have been clearly shown by placing
colored indicators at the level of the hypostome. In the days after the
marking, the colored area expands progressively towards the body column
and the basal disc.
In an early series of experiments, Brien and Reniers-Decoen (1949, 1950,
261
1960); Gallien (1965); Hartmann (1956); Burns (1955b, 1961); Russell
(1961); Bacci (1965); as well as comprehensive collections of reports: Sex
and Internal Secretions (Allen, 1934, 1939; Young, 1961); Colloques Internationaux du C.N.R.S. (1950); Intersexuality (Overzier, 1963); Intersexuality in Vertebrates (Armstrong and Marshall, 1964); Organogenesis
(De Haan and Ursprung, 1965).
II. Epigenetic Controls during Sexual Differentiation in the Invertebrates
The most significant recent work has been carried out on hydras (Coelenterata), insects, and crustaceans.
A. Sexual Differentiation in Hydras: Intersexuality
and Experimental Sex Reversal
Owing to the simplicity of their structure, the hydras have made possible
an experimental analysis of the essential aspects of the factors involved in
sexuality: relationship between blastogenesis and gametogenesis, origin of
germ cells, beginning of gametogenesis, and the sexual orientation of the
germ cells toward spermatozoa or oocytes (Brien, 1961, 1962a,b, 1963;
Brien and Reniers-Decoen, 1949, 1950, 1951, 1955).
For the hydras as a whole, genetic determination is considered to be
relatively labile. Although Hydra fusca is strictly gonochoric, H. attenuata,
which is normally gonochoric, has, by accident, an intersexual phase,
characterized in the female by the temporary development of testicular
structures in a specific region. In H. viridis, which is hermaphroditic, the
upper part of the body column develops testicular swellings, below which
are ovaries, while the base of the column develops buds under suitable
physiologic conditions (Fig. 1). This aspect of specific regions related to
sexuality must be emphasized. In addition the region under the hypostome
contains a supply of the interstitial cells that give origin to gametoblastic
and somatoblastic cells. Among the latter the cnidoblasts that give rise to
nematocysts are particularly interesting with respect to their cellular
differentiation.
Sexual function is linked to a very simple structure. The gametes differentiate from interstitial cells in swellings that rupture to liberate the
genital products. There is no reproductive tract. The development of the
egg is external.
The hydra is renewed constantly by wearing away of the pedal disc, and
the cells forming in the region of the hypostome proliferate and spread out
in the direction of the disc. These facts have been clearly shown by placing
colored indicators at the level of the hypostome. In the days after the
marking, the colored area expands progressively towards the body column
and the basal disc.
In an early series of experiments, Brien and Reniers-Decoen (1949, 1950,