H. B. Fantham 
389 
The shape of the epimerite in the trophozoite of Selenidium 
is variable. Caullery and Mesnil (1899) describe two forms of 
Selenid trophozoites with epimerites from Girratulus cirratus: (i) a 
comma-shaped variety (S. “ en virgule ”), and (ii) a semi-colon-like 
variety (S. “ en point et virgnle ”). This variation is discussed by 
Brasil (1907), who attributes the truncated aspect to an invagination 
of the anterior pointed region (Brasil (1907), pp. 376, 384, 385). 
Apart from the possibly injurious effect of the parasite upon the 
host cell, due to the organellae which serve for attachment, the in¬ 
vestigations of Brasil (1907, Fig. 14) have shown that the merozoites 
of S. caulleryi may issue in masses into the lumen of the gut, thus 
displacing the epithelium. 
It is interesting to note that species of Selenidium may in turn be 
parasitised. The Selenids of Phascolosotnes (Brasil and Fantham, 1907) 
as well as certain species of Selenidium in Polychaetes (Caullery and 
Mesnil), and the Platycystis (= Selenidium) of Leger in Audouinia all 
contain minute parasites, one stage of which has the characteristic 
morula-form (cf. Chytridiopsis of Aime Schneider). 
In the following section an attempt has been made to set forth 
a complete list of the various species of Selenidium (see p. 399). This 
has entailed much labour, and the searching of many papers and 
figures. Of the lists of hosts of Selenidium given by Labbe (1899, who 
retains Mingazzini’s name Polyrhabdina ) and Minchin (1903), two 
members must certainly be radically revised as regards harbouring 
parasites belonging to the genus Selenidium. Regarding one of these, 
that described by Greeff (1885) as Gregarina annulata from the intestine 
of Rhynchonerella fulgens, it must be noted that it is transversely 
annulate as figured in the original, and seems to have been referred 
incorrectly to Mingazzini’s genus Polyrhabdina. As at present under¬ 
stood, and pending further researches, Greeff’s parasite has no place in 
the genus Selenidium. The other parasite, described by Ray Lankester 
(1866) as Monocystis eunicae, has been referred by Labbe to the 
so-called genus Polyrhabdina. It was found in the gut of Eunice 
harassed, and is listed by Minchin in the geuus Selenidium. Reference 
to Lankester’s figure does not support the view that “Monocystis 
eunicae” belongs to the genus Selenidium, and the discoverer makes 
no mention of longitudinal striations being present. Pending further 
researches it should certainly be removed from the genus Selenidium. 
Most of the species at present placed in the genus Selenidium are 
ouly known in their trophozoite phase; further researches are greatly 
