A REMARKABLE ORUSTACEAN PARASITE. 109 
sections, which are flexed into the shape of a Z, the last joint 
being directed dorsally. Posteriorly to the antennez is placed 
the oral cone (or. ¢. of fig. 3) upon which the mouth opens, 
and in which lie a pair of weak crushing mandibles ; the latter 
were clearly recognisable in transverse sections, but their 
exact shape could not be ascertained. The oral cone is deeply 
grooved in the median line in a manner suggesting the fusion 
of two lateral plates. Behind the oral cone are placed six 
pairs of (thoracic) appendages (i—vi, fig. 3), of which the first 
are long, slender, and uniramose, the five posterior pairs being 
reduced to simple leaf-like flabella ; they are all devoid of hairs 
or spines. The body is then prolonged into a trumpet-shaped 
penis slightly bifid at the free end, which bends forward along 
the ventral surface between the appendages of the two sides. 
From the base of this projects backwards a bilobed knob prob- 
ably representing the abdomen; at this point commences the 
dorsal curvature, a slight segmentation being recognisable 
before the posterior junction of the carapace with the thorax 
is reached. 
The epidermis, a single layer of flattened cells, is covered 
over the whole surface of the body, carapace, and appendages, 
by a thin chitinous cuticle ; though a calcareous layer might 
have been removed by the action of the decalcifying fluid 
in which the Bathyactis had been placed, no histological 
evidence of such a deposit is forthcoming. The spines on the 
carapace are simply outgrowths of the cuticle and epidermis, 
and show no trace of a nervous or nutritive function. The 
perivisceral space underlying the outer body wall does not 
appear to be sharply bounded on the parietal surfaces. Mus- 
cles (striated), individual muscle-fibres, and connective-tissue 
strands run through it; at some points the parietal surfaces 
appear to be discontinuously lined by large roundish cells, of 
a markedly yellowish tint and very granular contents; it is 
possible that the discontinuity of this layer is due merely to 
the method of preservation. The splanchnic surfaces are 
lined by small flattened cells; no epithelial layer surrounds 
the muscles or generative organs. In the specimens drawn in 
