The Determination of Sex 271 
This means that in Diplogaster robustus there is 1 male to 
10,000 females, and in Rhibiditis viguieri 1 male to 450 females. 
There is nothing in the structure or in the organization of 
these superfluous males that would lead us to consider them im- 
perfect. In every point of their organization they correspond 
to the ordinary type of the males of unisexual species. Even 
the testis is normal and produces spermatozoa which are identical 
in form, size, and structure with those in the hermaphroditic 
glands of the corresponding females. On the other hand, these 
males have nearly lost their sexual instincts, and are rarely seen 
to pair with the hermaphroditic females. 
Maupas carried out the following experiments. He placed 
males and females together for a number of days and recorded 
the number of times fecundation took place. It will be observed 
that more that half of the cases occurred in Rhabditis marionis, 
in which it is known that the hermaphroditism is incomplete. 
FEMALES MALES FECUNDATIONS Days 
Rhoditis elegans 139 112 6 4to 9 
Rhoditis caussaneli 42 35 ° 5 to 10 
Rhoditis marionis 28 42 13 sto 7 
Rhoditis duthiersi 62 41 I 4to 6 
Rhoditis perrieri 26 35 ° 5 to 7 
Rhoditis duthiersi 12 5 ° 6to 7 
Diplogaster robustus 4 2 O° 4to 5 
: 313 272 20 
Thus 313 females put with 272 males gave only 20 fecundated 
females. In all cases except R. marionis the sexual indifference 
of the males is almost absolute. This is the more surprising, 
since in other species of Nematodes with separate sexes the 
copulation is readily observed and lasts for some time. Here, 
then, we have a case of a psychical “decadence,” unaccom- 
panied by structural degeneration. The sexual process is being 
replaced by hermaphrodite fecundation. 
This elimination of the male type in the Nematodes is shown 
