DR. W. C. M'INTOSH ON THE HAIRS OF CARCINUS MJENAS. 87 
single (2) and double hooks (3, 4, 5, ef seq.), and all the varieties of the compound unci- 
form conformation, as seen in the accompanying outlines (fig. 4). They are translucent, 
solid structures, clearly a development of the cortical substance of the hair. Most, but not 
all, of the simple ones are directed towards the base of the hair. It is difficult to assign 
Fig. 4. 
the exact function of these bodies on the hair, but it is probable that they may be of 
service to the Crab in denuding the branchial laminæ from parasitic structures, such as 
the minute zoophyte afterwards to be described. If any of the recurved hooks caught 
the root-portion of such a structure during the ordinary motion of the whip and its hairs, 
the parasite would most certainly be destroyed. 
Fourth pair of Foot-jaws.—The three sides of the fan-shaped organ, a, fig. 5, are sur- 
rounded by a fringe of beautifully feathered hairs, some long, others short, the former 
somewhat like those in Pl. XIX. fig. 10. They run in a very regular manner round its 
margin, and sometimes appear to be internal to it. Each hair has its little dark bulb 
and insertion, which lend to the hairy line a dotted or moniliform appearance. The 
hairs are largest on the outer edge, 5. The portion ¢ Fig. 5. 
has a very acute spine-like tip at the oral side, which a 
bears a slightly serrated bristle or two. Along the oral 
margin the hairs are mostly long and serrated; on the 
outer side they are less numerous, shorter serrated ones 
next the spine, but towards the outer part becoming 
feathered. Both kinds are often laden with parasitic 
structures. Some of the serrated hairs are peculiar, in 
that their serrations are coarser near the tip than they are lower down. The limb, d, 
conspicuous by its deep terminal fissure, has its oral end on each side of the ced 
covered with moderately long smooth hairs, with a few serrated ones. On the Mr 
next the two following there are none, while its opposite or convex margin has a g à y 
number of long serrated hairs. At the base of this portion two filiform processes m 
the upper or anterior of which, e, has a few serrated hairs on its surface near the tip, an 
a terminal tuft of some smooth and one or two faintly serrated ones. The lower pro- 
cess, f, has some smooth hairs on its posterior border at the base, and towards the tip 8 
the same side exhibits long, slightly dentated ones; on the tip itself are slightly serrate 
and long smooth hairs. 
N2 
