202 
Cricetomys gambianum 
and I. paronae Bischoff 1912, and in Zschokkeella the species Z. linstowi 
(Parona 1900), Z. muricola Baylis 1915, Z. gambianum (Beddard 1911), I. 
capensis Beddard 1912, and Th. lemuris Beddard 1911. In the remaining 
species the behaviour of the uterus has not been described and therefore they 
cannot be ascribed to either genus. A difference in the formation of the egg- 
capsules, as Beddard has pointed out, is hardly sufficient to distinguish 
two genera but, failing this, Inermicapsifer must fall into synonymy 
with Zschokkeella as no other character exists by which they can be distin¬ 
guished one from the other. Until, therefore, a more detailed account of the 
behaviour of the uterus throughout the group be published it seems best to 
leave the two genera separated by this difference. 
In accordance with this decision the new species described at the com¬ 
mencement of the paper (p. 193) belongs to the genus Inermicapsifer and bv 
means of the table on pp. 200-201 can be distinguished from the other species. 
I propose for it therefore the name Inermicapsifer zanzibarensis n.sp. 
Dipylidium oerley von Ratz, 1900. 
The material of this species from the cat consists of three strobili and a 
few isolated proglottides. The greatest length observed was 40 mm. and the 
greatest breadth 1 mm. A scolex was not present. 
The musculature of the mature proglottides (PI. IX, fig. 1) in a transverse 
section consists of three longitudinal muscle bands, each bounded internally 
by transverse muscles. The innermost longitudinal muscle layer is composed 
of numerous small bundles, clearly separated one from the other, and formed 
by the aggregation of small fibres into groups of from 2 to 5: this layer, while 
distinct in the more posterior portion of the strobilus, becomes less marked 
anteriorly, until in proglottides with feebly developed male organs it entirely 
disappears. The layer external to it is wider and more continuous, the bundles 
are larger and formed of more fibres (approximately 20) and, together with 
the third layer, it is persistent throughout the proglottis. The outermost 
longitudinal muscle band is composed of numerous muscle fibres, aggregated 
into bundles of 5-8 internally and continuing as isolated strands nearly to the 
sub-cuticula. The transverse muscle layers are very irregular and vary greatly 
in appearance, occasionally disappearing altogether. 
The excretory system in mature proglottides consists of a single large 
longitudinal vessel on each side, the two vessels communicating by the usual 
transverse commissure at the posterior end of each segment. 
The genital pore is usually situated in a conspicuous depression in the 
anterior half of the proglottis margin; occasionally the depression is partially 
evaginated, becoming a small protuberance. The genital ducts pass dorsal to 
both excretory vessels and to the nerve. The cirrus-sac is 0-21 mm. long x 
0-08 mm. diameter and extends just past the excretory vessels. Its muscula¬ 
ture is very feeble and special retractor muscles are absent. The cirrus is 
