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84 DR. W. C. M'INTOSH ON THE HAIRS OF CARCINUS MJENAS. 
At the outer ridge of the first segment of the accessory limb, g, there is a row of short 
but strong hairs of the branched kind, abounding in parasitie appendages. On the 
dorsal surface is found a row of branched hairs near the oral or inner margin, from the 
base forward to the anterior edge, where they end in a projecting spike, which is covered 
with a long tuft of the same hairs. On the ventral surface there are few hairs, and the 
minute cuticular bodies are scarce. The delicately jointed process which is attached to 
the extremity of this segment has its hairs mostly of the branched form. After passing 
the sickle-shaped portion, A, they run in a double row along one side of the flabellum 
to the tip, two on every joint; and they increase in length as they approach the 
extremity. In the ordinary state of the Crab these hairs are much covered with 
extraneous growths. The filmy forms, resembling minute fungi, abound, and, together 
with the other parasites, make the hair more impenetrable than a thickly coated feather ; 
just as the climbers of the tropical forests weave neighbouring boughs into one imper- 
vious web. Each seta of the branched hairs is coated with its load of growths; nor are 
the simple hairs exempt from a like covering. In the newly-moulted Crab they are clean 
and distinct, and, like those subjected to nitric acid, show a somewhat jointed aspect at 
the tip and for some way down. 
The hairs of the branchial whip pertaining to this foot-jaw are large and powerful, 
their tips being finely serrated. They have a well-defined central space, filled with 
cellulo-granular materials. Just where the serrations begin, there are several large 
canine-like fangs, far surpassing the rest in size, and curved in a contrary direction or 
towards the root of the hair. Many are covered with dark parasitic masses, from which 
shoot transparent filmy threads of gossamer fineness, and amongst which Infusoria and 
other Protozoa lurk. The observation of the latter, indeed, would be a study of no mean 
extent; and the'natural history of these companions and satellites of Carcinus menas is 
calculated to excite wonder by their number and interest. Most of these hairs are not 
terminated by a sharp point, but end in a somewhat strong tip, a state probably more 
suitable for the due performance of their functions (see Pl. XIX. fig. 5). A row of 
hairs along the sharp ridge of the thin lamina to which the base of the whip is attached 
is composed of hairs similar in structure, but of much smaller dimensions; they are also 
frequently covered with parasitic masses. The other hairs on this lamina do not differ 
so much as to require separate mention. 
Second pair of Foot-jaws.—The tip of the strong limb, a, fig. 2, is protected by a series 
of thick-set bristles of a highly striated aspect, best seen after sub- Fig. 2. 
jection to nitric acid. They terminate in blunt points, which give d 
them an aspect of hard service; but this is not the case, since they are 
not much sharper in the soft Crab (Pl. XIX. figs. 6 & 8). Interspersed 
amongst these vigorous cutaneous appendages are others of smaller 
size, but of similar structure. The hairs on the margins and general | 
surfaces of the last three segments, a, b, and c, are serrated, but not 
deeply.. A few feathered ones are now and then met with, but they 
do not influence the general picture. The long segment, d, has a mix- 
ture of serrated and branched hairs on its inner margin. A few hairs 
