Haswett—A Monograph of the Teninocephatlee. 111 
third of the breadth of the body, and, in its thickest part, four-fifths of the thickness. 
Its dorsal and ventral walls are thicker than its lateral. It contains a cavity which, 
probably rounded in the distended, is usually compressed and tri-radiate in the 
contracted condition. Its internal lining membrane is a thick layer of almost 
homogeneous character, very finely granular and very finely striated in a vertical 
direction —the striz appearing under a high power as rows of dots. This layer is 
not cuticular in character, and, though devoid of nuclei, must, I think, represent the 
internal epithelium. A continuation of the surface epithelium into the interior of 
the pharynx as deseribed by Weber is not recognisable im my sections ; but in some 
there appears to be a very thin inner layer, which may be an internal cuticle. The 
greater part of the wall of the pharynx is composed of muscular fibres which are 
readily distinguishable into the following layers.* Most externally is a complete 
coating of circular (transverse) fibres ; and most internally next to the epithelium is 
an internal layer, the fibres of which run in the same direction. Between those 
extend numerous radial fibres arranged singly or in narrow bundles ; these are 
separated from one another by interspaces containing parenchyma; each splits up 
both externally and internally into several branches. Running between the outer 
ends of these radial fibres are the fibres of a thin external longitudinal layer, and 
a similar longitudinal layer runs between their inner ends. At the anterior and 
posterior ends of the pharynx very closely arranged circular fibres fill the interspaces 
between the radial fibres and to a great extent displace them; slender radial fibres 
divide those into tolerably regular bands.t Strands of parenchyma muscle passing 
from the outer circular layer towards the integument have probably the function of 
protractors and retractors. 
Between the muscular layers there runs a system of visceral nerves, with 
oceasional bipolar ganglion-cells, to be afterwards referred to. 
In the wall of the pharynx between the radial muscular fibres are numerous 
large cells with processes, which in some instances anastomose. They have large 
nuclei—0175 mm. in diameter in 7. fasczata, smaller in 7. Dendyz, with a single 
rounded nucleolus in the former case, and with several small chromatin masses in the 
latter. In the latter species these cells send processes inwards between the radial 
muscular fibres, forming narrow ducts along which a bright oily-looking secretion 
passes to enter the internal cavity of the pharynx. These ducts were not seen in 
the other species ; but it is not likely that they are absent. The cells are thus of 
* In my former paper there is an unfortunate mistake in the account of the layers of muscle in the wall of the 
pharynx. Fig. 6 of Pl. xx. is a drawing of a part, not of a /ongitudinal (as stated in the explanation of the plates), but of 
a transverse section, and in the account of the arrangement (p. 290) the order of the layers is reversed in accordance with 
this. The thick anterior and posterior masses of circular fibres were overlooked altogether. 
+ These correspond to the much less strongly developed ‘‘ sphincter” fibres found by Bohmig in the pharynx of 
Plagiostoma Lemani ; but the term sphincter, owing to their extent, is not applicable to them in the case of Temnocephala. 
