194 
Cricetomys gambianum 
in tlie present species, as in many tapeworms of the group Tetracotylea which 
I have examined, the sucker does not lie externally on the scolex, but is 
covered by a layer of body-wall which is only interrupted at the orifice of 
the sucker. The free edge of this, when depressed towards the interior of the 
sucker, is doubtless funnel-shaped and would give rise to the appearances 
represented by Janicki. Perhaps, however, there is some divergence from the 
normal condition of the suckers in the members of the genus referred to by 
him, which I certainly have not found in the species with which I am at present 
concerned.” The suckers figured by von Linstow (1906, PI. XIII, fig. 9) for 
Z. remota and Pagenstecher (1878, PI. X, fig. 2) for /. crilicus are obviously 
on the surface of the scolex in the usual Cyclophyllidean position. In Z. muri- 
cola , according to Baylis (1915, 41), they occupy an intermediate position, 
“they are sunk somewhat deeply in the substances of the head, and their 
orifices are flush with the surface.” My own observations confirm the state¬ 
ment of Beddard just quoted. The suckers are distinctly under the surface of 
the scolex but not at the bottom of the funnels and they thus present a very 
different appearance to the usual Cyclophyllidean sucker with a rim of muscu¬ 
lature on the external surface of the head. The greatest diameter of the suckers 
observed was 0*2 mm. Behind them the scolex bulged to a considerable extent, 
its posterior limit being twice the diameter of the long unsegmented neck 
which follows it. The proglottides are broader than long for the greater part 
of the strobili, the more terminal ones being approximately square. 
The musculature of each proglottis (PI. IX, figs. 5-7) is exceedingly weak, 
consisting of only two layers, one transverse and one longitudinal. The latter is 
composed of a number of isolated fibres—only occasionally do two or three of 
them become aggregated together into a bundle—scattered irregularly through¬ 
out the cortical parenchyma. Internally to them lie several strands of trans¬ 
verse muscles forming a band enclosing the genital organs and medullary 
parenchyma. 
The excretory system consists of the usual four longitudinal vessels, two 
on each side of the proglottis—these being arranged laterally to each other 
instead of dorsally and ventrally. The innermost is large and thin-walled and 
communicates with its fellow of the opposite side by a large transverse com¬ 
missure at the posterior margin of the proglottis. It also gives off here an outer 
vessel the branches of which, running anteriorly, anastomose with each other 
and with the parent stem, forming a small excretory plexus. The outer longi¬ 
tudinal vessel is small and thick-walled, gives off no lateral branches, and does 
not communicate with that on the opposite side by any transverse commissures. 
The genital pore is unilateral, nearly at the anterior quarter of the pro- 
glottis margin (PI. IX, fig. 4). A small and narrow genital cloaca is present 
and into it open anteriorly and posteriorly the cirrus-sac and vagina respec¬ 
tively. The genital ducts pass between the excretory vessels and—assuming 
the larger excretory vessel to correspond to the ventral vessel usually present 
and the smaller to the dorsal—dorsal to the nerve. 
