86 DR. W. C. M'INTOSH ON THE HAIRS OF CARCINUS MJENAS. 
powerful and comparatively short, most being slightly serrated—some nearly throughout 
their whole extent; towards the base of the segment they become more slender, though 
also serrated at the tip. "There are generally a few smooth hairs here and there amongst 
these and on the general surface of the segment. At the base of the external margin, 
and for some way up, are feathered hairs. There is a row of smooth hairs, c, on the 
ventral surface, short and interrupted towards the tip of the organ, but afterwards 
becoming denser and more continuous. In re- Fig. 3. 
gard to the rows of strong hairs generally, it 
is found that there are a number of smaller 
hairs or hair-roots always present at the one side 
of the series, so as to blend them gradually with 
the general surface of the organ, or else to sup- 
plant the others in cases of necessity. 
On the accessory limb, d, the anterior broad  . 7 
margin is covered with long slender hairs mi- ^ - 
nutely serrated at the tip. "Towards the inner sharp end they become broadly feathered. 
Seattered amongst the roots of the larger hairs are some small, simple, and a few short 
feathered ones. Having begun at the inner sharp anterior angle, the line of the hairs 
splits, one well-marked series of feathered ones continuing along the oral edge, after 
passing the oblique portion common to both, to the base. Some are most powerfully 
bristled, the latter appendages being of considerable bulk themselves. Interspersed with 
them are some short, simple, and a few serrated ones, the latter, however, generally 
possessing bristles also. The other line (dorsal), which starts from the inner anterior 
angle likewise, has only a few short, smooth, and some feathered hairs, and soon dis- 
appears. At the base of the outer margin of this limb is a short row of spiked hairs. 
At the delicate extremity of the elongated organ to the outer side, the hairs are 
feathered in the same manner as those of the analogous structure in the previous pair of 
foot-jaws ; and the tip, e, is sketched in Pl. XIX. fig. 10. In the soft Crab they are best 
shown, as they are free from confusing parasitie structures, and possess the usual joint- 
like structure, with the central portion bounded by a somewhat wavy internal line. The 
thinness of the cuticular layers and the large size of the base of the hairs, which 
evidently have an intimate connexion with the cavity of the limb, would all favour the 
use of these hairs in regard to sensibility, as has been shown by Lavalle, De Morgan, 
. and others. On the anterior or convex portion of the projecting sickle-shaped base, f; 
there are a few thinly spiked hairs, some serrated ones and some smooth. Along the 
outer margin of the segment, g, the hairs are chiefly of the feathered variety ; they 
occur in two sets, one at the distal extremity and for some way down, the other at the 
base. They are of much smaller size than those on the tip. The inner edge is rather 
seantily supplied with short smooth hairs, principally present near the base. 
The extremity of the branchial whip, m, is covered with serrated hairs of considerable 
strength ; they are of the same structure all the way down, the only variety worth 
noticing being some of smaller size, and wanting the recurved fangs. The latter, 
speaking generally, vary considerably in form from the simple tubercle (1) to the 
