A PARASITE OF THE TIGER SHARK. 
547 
lying parallel with each other. In longitudinal sections made parallel 
with the face of a bothrium, some of them are seen in cross section. 
The cuticle of the body is a very remarkable structure. In superficial 
view, especially in a stained specimen, it appears to be scaly or, more 
properly speaking, minutely ajid irregularly tessellated, since the 
pieces do not break joint (figs. 24c and 33a). 
In section the cuticle is seen, when highly magnified, to be made up 
of three distinct layers. These may be described as an outer epidermal 
layer, an inner epidermal layer, and a third limiting layer, the cutis 
(figs. 21a, 27, and 31). 
The outer epidermal layer under high magnifying power shows a 
densely striated structure, the striae being at right angles to the super- 
ficial extent of the layer. The inner epidermal layer appears very finely 
granular and usually almost homogeneous. In some especially good 
sections, however, fine striae were seen in it. These also lie at right 
angles to the layer, but are not close together as in the external layer, 
and the interstices are filled with fine granular material. The epidermis 
rises in folds from a very thin limiting membrane, the cutis, to which 
the fine radial fibers of the subcuticular granulo-fibrous layer are at- 
tached (fig. 21a). 
The outer epidermal layer is uniform in thickness ; the inner layer 
is irregular in thickness, rising from a comparatively uniform base, 
where it touches the cutis, into papillae which conform to the folded 
structure of the outer layer. 
A few small granular patches, of glandular appearance but of un- 
known significance, were observed in this layer (fig. 31a). 
The epithelial origin of the hooks of the scolex is shown in fig. 13. 
In unstained specimens treated with caustic potash the hooks appear 
transparent and homogeneous. 
The hooks in this species differ from the chitinous hooks of such 
genera as Calliobothrium in that they are solid and not characterized by 
having an internal cavity. The epidermal layers of the body do not 
extend, at least unmodified, into the pseudoscolex. 
The external folds of the pseudoscolex appear in section as fimbrim, 
about 0.02 mm in dia meter. The folds are seen to be limited on each side 
by a thin, uniform layer, apparently structureless and about 0.002 mm 
thick. This layer appears to be continuous with the cutis of the body. 
In the deeper parts of the folds, that is, toward the center of the pseudo- 
scolex) this cuticular layer becomes somewhat thickened and is irreg- 
ular or broken on the surface. In some cases it was seen to bear on its 
outer surface what appeared to be a dense coat of epithelial hairs. 
This cuticular layer is in close connection with the longitudinal mus- 
cles of the body, which extend, mostly as radial fibers, into the pseudo- 
scolex. It is itself apparently contractile. Indeed, it and the cutis of 
the body may subsequently be shown to belong to the subcuticular layer. 
Internally the external folds of the pseudoscolex are composed of 
