DR. W. C. M'INTOSH ON THE HAIRS OF CARCINUS MJENAS. 83 
collected in small patches, as in other portions of the same animal. It may be here 
mentioned that, besides the hairs on the investment of the Crab, there are a number of 
minute processes, in the form of sharp spicules, which project from the cuticle, occur 
most abundantly in the neighbourhood of hairs, and are absent from the papille of the 
cutis (Pl. XX. fig. 20). They are easily seen on this portion by softening it in dilute 
nitric acid, and removing the external layers of the shell by tearing a fragment with the 
forceps. They are well marked in the soft Crab, and are found fully developed on the 
soft carapace of those having the old shell still adherent. 
Along the anterior margin, c, two kinds of hairs are met with, the feathered or spiked, 
and the smooth. There are none of the serrated variety. A peculiar brush-like 
appearance, not unlike a miniature Thuiaria thuja, characterizes many. One or two are 
covered with very long branches which slope gently from their sides (Pl. XIX. fig. 3). 
The first joint (basal) of the terminal appendage, e, which succeeds, is covered with long 
hairs, those on the anterior edge being most excellent specimens of the feathered variety. 
Some smooth ones are also found, chiefly congregated in a long tuft at the beginning of 
the row, û. e. next the base. The ventral surface of this portion abounds with the minute 
sharp bodies mentioned previously, and they darken the cuticle under the microscope. 
The addition of caustic potash brings out these bodies as sharp, slightly curved spikes. 
There are a considerable number of cuticular apertures for papillze on this surface. On 
the inner or dorsal aspect (the animal being in its normal position) there are none of 
the minute cutieular spikes over the general surface, and only a few blunt projections 
near and amongst the hairs. The papillee were generally found in the same region. ‘The 
hairs are pale and mostly serrated—in short, presenting the latter arrangement in perfec- 
tion. The serrations vary, some being close and small, others large and distinct; but 
both are very interesting microscopie objects. ٠ 
The next segment is covered on its inner or dorsal surface with many strong bristles, 
which have the serrated character strongly marked. Some of the serrations are large, 
blunt, and broad, others sharp and narrow, while a third set are intermediate. An 
oblique view of part of one is given in Pl. XIX. fig. 2, where the teeth are seen on their 
most extensive surfaces. On the ventral surface the hairs are much smaller, but also 
serrated. The cuticular areole of Profs. Huxley and Williamson (cells of Profs. Carpenter 
and Quekett) are generally bolder and better-marked on exposed surfaces such as the 
present. The tuft on the terminal division is composed of finely-set serrated hairs of 
strong formation ; indeed, when viewed laterally, they call to mind the incisive bones of 
a well-armed Pristis. A few short smooth hairs, and some of smaller size and more 
finely serrated than the former, also occur. 
Attached to the base of the great foot-jaw is a large accessory limb, whose terminal 
portion consists of a flabelliform appendage of delicate proportions, jointed and covered 
with hairs. Those of the basal portion, f; from which both this accessory limb and the 
foregoing part of the foot-jaw spring, are mostly in two rows; one, the thickest and 
longest, slants over the ventral surface, while the other crests the anterior ridge. They 
are branched, and often quite darkened by parasitic structures. On the external surface 
there are numerous well-marked microscopic cuticular spikes. 
