374 Mr Potts, Sexual Phenomena in the Free-living Nematodes. 
On decay these are found to contain thousands of living and 
breeding nematodes. 
The hermaphrodite species occur in my experience at least 
as frequently as the bisexual forms, and in general are easily 
adaptable to culture methods. Solutions of peptone were adopted 
as convenient culture media ; while allowing close observation of 
the processes of development, they constitute so favourable an 
environment for growth that the whole duration of a generation 
is only from ten days to a fortnight. It is, however, only the 
putrefaction products of the peptone on which the nematodes 
thrive so well ; in sterile solutions growth is suspended and ovi- 
position proceeds only with great slowness. 
The species under observation were mostly inedited ; there 
can be little doubt that the researches of Bastian, Schneider, 
de Man, etc. have not revealed a tithe of the species of free-living 
nematodes. The most extended series of observations was made 
on a hermaphrodite species of Diplogaster, which strongly re- 
sembled a bisexual species described by earlier authors. It may, 
perhaps, be suggested that in the future complemental pairs of 
species may be found to exist, the bisexual form and the herma- 
phrodite derived from it. 
In the course of research single individuals were, as far as 
possible, isolated in each generation and the constitution of their 
progeny examined. It is considered that these precautions not 
only prove that the supplemental males really belong to the 
species and are not merely due to accidental infection with bi- 
sexual species, but also render possible an exact analysis of the 
proportions of the sexes. 
The supplemental males occurred throughout the cultures and 
could be recognised as belonging to the same species as the 
hermaphrodite form, by the structure of the buccal cavity. They 
possessed a copulatory bursa and spicules, fully formed and of an 
identical type in all those examined. Not only did their structural 
organisation appear perfect, but they were observed to be capable 
of even more energetic movement than the hermaphrodites. But 
though the genital gland and duct was packed with spermatozoa 
in various states of development, which, when mature, exhibited 
amoeboid movements (and were thus apparently capable of the 
work of fertilisation), the males seemed to have lost their sexual 
instinct. This “psychical decadence” of the males, as Maupas 
phrases it, though marked, was not complete, for one out of the 
many whose behaviour with hermaphrodites Avas observed Avas 
seen in copulation. It was concluded, hoAvever, that the results 
of such union must, in the present case, always be unfruitful 
and that the males are an entirely unnecessary factor in the re- 
production of this nematode, 
