82 DR. W. C. MSINTOSH ON THE HAIRS OF CARCINUS MJENAS. 
segment, û. Those at the base of this organ are greatly brushed, especially towards the 
terminal half of the hair, as shown in Pl. XIX. fig. 1. 
A peeuliar marking is observed at some distance 
from the insertion, after which the setze of the hair 
become far more numerous. It indicates, in fact, 
the point where the brush-like covering of the hair 
supersedes the more scanty bristles. Some of their 
points are bristled to the tip, others are smooth, 
while fungoid growths obscure not a few in the - 
perfect condition of the Crab. In some cases, the 
spikes at the base of the hair are very sparsely distributed. By the side of the raised line 
of shell, towards the oral margin on the ventral aspect (at the inner end of the dotted 
line from b), there is a row of hairs with smooth shafts and serrated tips. The external 
margin of the segment has numerous short serrated ones. Dotted at somewhat regular 
intervals near the internal margin of the dorsal surface are groups of short smooth hairs, 
with a peeuliar marking towards their middle, as if jointed. "Towards the outer margin 
of the same side are a considerable number of short hairs, smooth, slightly bristled or 
serrated. In several parts of this segment, especially on its ventral surface, the papille 
of the cutis and the groups of hairs are in rows together. 
On the irregular segment, c, fig. 1, beyond this, the following arrangement exists. 
Along the dorsal margin of the somewhat triangular groove in which the joints settle 
when folded, there is a conspicuous row at d. Most of these are covered with long 
spikes, which everywhere stud their surface and give them a beautiful feathery aspect. 
Amongst them, however, is one, a short piece of which bears no distant resemblance to a 
head of wheat with its elliptical chaff (Pl. XIX. fig. 2). The peculiar appendages appear 
to be modifications of spikes, and there is a double row on each hair. Sometimes, from 
the position of the latter, there seems to be only one; but on closer examination, the 
other is seen to be shaded by the contour of the central stalk. In the interval between 
the serrated margins of the hair, a series of short bristles frequently occurs. The basal 
or root portion of the hair is smooth for a considerable way up ; the serrations then begin, 
small at first, afterwards swelling out into full proportions, and gradually diminishing 
again as the hair tapers to its termination. Most of such hairs are stronger than the others, 
and they are seen to best advantage in the soft state of the Crab. The brushed hairs of 
this part often have a plentiful supply of fungoid growths and other external appendages. 
The opposite or ventral margin of the before-mentioned pit has very short brushed hairs, 
with a few feathered ones at each end; and following the course of the ridge which runs 
obliquely outward from this are some short serrated ones. The cuticle on the ventral 
surface of this segment is sparsely studded with small hairs, and the tubuli seem to be 
examined a small transparent Palemon from the South Pacific, also considers that the internal antennee contain the 
auditory organs, but no mention is made of the outer antennae (Ann, & Mag. Nat. Hist. vol. vii. 1851). 
I have endeavoured to test the true function of these organs by experiments on living animals, but the results are by 
no means definite ; indeed, after the removal of both internal and external antenne and the organs at their base, 
together with the eyes, the animals started sharply when the glass vessel containing them was struck. | 
