W. Heape 
221 
representing the spiral, though not so clearly as could be seen in the 
specimen itself. 
It is to be remarked that the clearest demonstration of spiral 
contraction is seen in the dorso-ventral fibres, which are attached at 
both ends, and that in these perhaps the most obvious spiral occurs on 
either side of the nucleus and close to it. This of course is the thickest 
portion of the fibre, but spiral contractions are clearly to be seen 
both in the two branches into which it first divides, and also in the 
four very fine tendrils into which these ultimately divide. 
Thus it may fairly be assumed that this power of contracting 
spirally is not due to any differentiation of the fibre itself but is an 
inherent property of the tissue. 
The spiral contractions of the circular fibres are less easy to 
determine because of the difficulty of following each fibre in the 
bundle, they are much finer than the dorso-ventral fibres, but in 
certain instances (Fig. 3) the spiral condition is clearly seen. For the 
same reason I have not found it possible to assure myself that these 
circular fibres split up into branches and indeed am disposed to doubt 
that they do so. 
The longitudinal fibres I have not been able to examine in a 
contracted state in my osmic acid preparations, for all the proglottides 
so preserved have, so far as I have seen, been stretched longitudinally; 
while in the corrosive and acetic specimens these bundles of fibres are 
not clearly shown. It is to be noted however that I have seen no 
nucleus in connection with them. 
Thus the main interest of this communication lies in the structure 
and behaviour of the circular and dorso-ventral fibres; at the same 
time the similarity in appearance and in consistency of the dorso-ventral 
and longitudinal fibres in the osmic specimens, and the similar effect 
which acetic acid has on them both, makes it extremely probable that 
all the contractile fibres in the body are of the same kind. 
In general all the contractile fibres of the cestoda are described as 
muscles, as for instance by Schmidt (1888, p. 155), though Moniez 
(1881) referred to them as differentiated fibres which form the so- 
called muscles of these animals. Pintner (1881, p. 163) specially 
described the dorso-ventral fibres, and calls them smooth muscles 
contracting in wavy lines, with a nucleus in the sheath in a non- 
contractile portion of the muscle. 
Hamann, in a paper on T. lineata (1881, p. 718) described for that 
animal;—an outer layer of longitudinal muscles arranged in bundles 
