Mr Potts, Sexual Phenomena in the Free-living Nematodes. 373 
Sexual Phenomena in the Free-living Nematodes. (Preliminary 
note.) By F. A. Potts, B.A., Trinity Hall. 
\Read 11 November 1907.] 
Attention has been drawn by Maupas 1 to the remarkable 
sexual conditions which occur in the free-living nematodes Rhab- 
ditis and Diplogaster. While some species of these two genera are 
bisexual, males and females occurring in equal proportions, others 
are composed of self-fertilising hermaphrodites, whose genital 
gland produces, first spermatozoa, then eggs which are fertilised by 
the male gametes as they pass one by one into the uterus. Large 
cultures of nematode species of this latter class are found to contain 
occasional male individuals, but though these possess a complete 
spicular apparatus for copulation and produce large quantities of 
spermatozoa, they are sexually inactive and entirely superfluous 
in the economy of the species. 
Maupas regards these supplementary males as the remnants 
of the whole male sex, while the hermaphrodites of the same 
species represent the female sex, from which they are derived 
by the substitution of a functional hermaphrodite gonad for the 
ovary, thus rendering the agency of the male sex unnecessary 
in reproduction. The occasional reappearance of males is cor- 
related with the incompleteness of the hermaphroditism. In all 
species studied it was found that there was an insufficient pro- 
duction of spermatozoa in the individual ; when this stock was 
exhausted the animal continued to lay unfertilised eggs which 
degenerate. Maupas was also able to describe species in which 
the hermaphroditism was incipient ; in one horn of the genital 
gland spermatozoa and consequently fertilised eggs were produced, 
while in the other the gland was purely female and unfertilised 
eggs only were traced back to it. In such nematodes the per- 
centage of supplemental males though low was markedly higher 
than in the species where hermaphroditism was more complete. 
The object of the present communication is to set on record a con- 
firmation of that part of Maupas' results summarised above. 
Free-living nematodes, of the two genera mentioned before, 
exist wherever sufficient nutrition can be obtained from decaying 
organic matter. Many species have been found in samples of 
vegetable mould from various localities, the method of obtaining 
them in quantity being to expose pieces of meat on the surface. 
1 “Modes et Formes de Reproduction des Nematodes,” Arch. Zool. Exper. et 
Gen. T. 8, 1900, pp. 463—624. 
VOL. XIV. PT. IV. 
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