H. B. Fantham 
387 
host under investigation was the Polychaete worm Dodecaceria con- 
charum, and it contained two parasites, one in the coelom known as 
Gonospora longissima, and the other in the gut, known as Selenidium 
echinatum. Caullery and Mesnil apportioned the schizogony, which 
occurred in the gut epithelium, to the former ( Gonospora ). Brasil 
(1907, pp. 389—393) discussed the matter at length, and considered 
that the schizonts really formed a part of the life-cycle of S. echinatum. 
Intra-epithelial schizogony also occurs in the Selenidium described by 
Caullery and Mesnil from the gut of Scololepis fuliginosa. 
The most detailed account of schizogony in a Selenidium is that 
given by Brasil (1907) for S. caidleryi , from the gut of the Polychaete, 
Protula tubularia. Brasil’s researches on S. caidleryi have been 
summarised in the preceding section (see pp. 376, 377, and Fig. 3, 
in, iv, v). 
Further researches on the schizogony of Selenids were published 
by Brasil and Fantham (1907) who studied species found in the gut of 
Phascolosomes (Phascolosoma vulgare and P. elongatum). Two species 
of Selenidiidae occur in these Gephyreans ; the species are differentiated 
at present by the number of longitudinal myonemes occurring in the 
respective trophozoites (Fig. 7). In the first species (a), which is 
rectangular in section, each face has only some two or three myonemes 
(Fig. 7, A, B) which are broad and very apparent. Two forms are 
recognised in this species, one with elongate trophozoites (Fig. 7, A), 
whose breadth is about one-fifteenth of its length, and which may 
reach 350 g in length, and the other, a shorter, stumpy form, whose 
breadth is about one-third of its length (Fig. 7, B). The nucleus of 
the elongate forms is nearly spherical (Fig. 7, A), that of the stumpy 
form is transversely ovoid (Fig. 7, B). Intermediate forms, however, 
occur between these elongate and stumpy types. 
The second species (/3) possesses many fine, longitudinal myonemes 
(Fig. 7, C, D), some 30 to 40 in number, while the body is circular 
in section. Elongate (Fig. 7, C) and stumpy (Fig. 7, D) types occur, 
but the differences in length between them are not so marked, and the 
relation of the breadth to the length is never less than one-eighth. 
Schizogony occurs in the epithelium of the gut of the Phascolosomes. 
In the deeper parts of the gut epithelium, the schizonts form oval cysts 
which project slightly into the coelom. Each schizont gives rise to 
some 30 to 40 merozoites measuring about 12/x in length. Lateral 
association has been seen between the Selenids with fine myonemes 
(Fig. 7, E). 
