Pleurocystis cuénoti, Hesse. 209 
inadequate figure. In Monocystis agilis and other species 
the application of the conjugants is polar or ‘ end-to-end ”’ 
(fig. 2). Since the parasites are attached to the seminal 
funnels of the hosts permanently, as all agree (and they do 
not become detached post mortem), it is the close proximity 
of the individuals to one another which determines their 
association into diploids inter se, which must therefore of 
necessity be longitudinal. A curious confirmation of this is 
shown in fig. 8 in the case of the diploids D and H, which 
are partially attached to one another at their posterior extre- 
mities, from which I infer that diploidal association probably 
always begins at this end. 
Pleurocystis cuénoti. Two diploids, D and E, partially attached to one 
another at their posterior extremities, 
But Hesse (1909) pointed out that Monocystis magna, 
Schmidt, differed so materially from other species that he 
proposed for it the generic name of Nematocyst’s. Further, 
that there was existing another animal, which, agreeing in 
the main with the characters of Monocystis rather than with 
those of MNematocystis, became coupled, in a longitudinal 
manner, with a partner for life like Mematocystis, and not 
merely during the process of conjugation. To this form he 
gave the name of Pleurocystis cuénoti, aud, while admitting 
that it is very rare, remarks that the animals are always in 
the diploidal condition and never found singly, After giving 
