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Stephanochasmus Looss 
shape, is made up of three regions: a thick basal disc (Fig. 8, 2), which 
lies near the outer surface of the cuticula, a thick-walled ring at the 
opposite side (36), through which the spine projects, and a middle 
portion which contains the broad inner end of the spine and appears 
lighter in colour than the other two portions. The spine is composed of 
a lighter coloured inner substance, and a darker periphery which is 
very thin and appears beaded (Fig. 8, ll). 
These specialized spines are found throughout the entire extent of 
the cirrus (with the exception of the extreme anterior portion) and the 
prostate region. A short distance anterior to the vesicula seminalis 
they suddenly come to an end and the cuticula contains the cuticular 
bristles alone. 
The musculature of the cirrus is not the same in all parts of it and 
enables us to divide the cirrus into two portions, the anterior, muscular, 
extrusile portion, which functions as the penis, and the posterior 
portion in which the muscles are weak. The musculature of the 
anterior portion is a continuation of that of the genital sinus and 
consists of rather delicate circular fibres (Fig. 6, 4) and a layer of powerful 
longitudinal fibres (22), which have a more or less rectangular cross 
section. The function of these strong longitudinal fibres in both cirrus 
and genital sinus is undoubtedly to thrust the cirrus out of the genital 
pore. They are the strongest towards the anterior end of the cirrus 
where they are a direct continuation of the longitudinal muscles of the 
genital sinus. Towards its posterior end they diminish in size and a 
short distance back of the acetabulum have the appearance shown 
in Fig. 7, 22. Still farther posteriorly both longitudinal and circular 
muscles become still less prominent and finally fade away altogether, 
or at least become difficult to demonstrate. 
The function of the cuticular bristles and the cuticular spines of 
the cirrus is not easy to determine. In the extended cirrus they extend 
into the lumen with a general backward direction and would thus tend 
to check the flow of sperm towards the outside. Their function may 
be to prevent the too rapid emission of sperm. 
The vesicula seminalis occupies the hinder portion of the cirrus 
sac (Figs. 1 and 2, 45). Its walls consist of a cuticula and muscle 
fibres. The cuticula is mostly plain and smooth and without the 
bristles or spines which characterize the cirrus. That of the anterior 
portion of the vesicula, however, shows transitional stages between 
the condition found in the cirrus and that of the vesicula. 
The metraterm (24) has a structure which is essentially similar to 
