80 DR. W. C. M'INTOSH ON THE HAIRS OF CARCINUS MANAS. 
it. Numerous other forms cluster around the hair—large and soft bodies of a cellular 
nature, Infusoria and other Protozoa, as well as many anomalous structures." However 
unlikely it may seem, it is by no means improbable that this circlet of hairs, when 
rendered more or less impervious by fungoid growths and mud-particles, may form an 
accessory sucker-arrangement by which the compound eye may be most powerfully 
retained in its socket. In addition to their giving a certain amount of sensibility to the 
calcareous cone on that side (a state all the more necessary since this Crustacean is liable 
to be attacked in this region by young specimens of the bearded Mussel), these hairs 
doubtless, too, serve as a buffer to the delicate organ when it is rapidly drawn in. 
Hairs of the External Antenne.—The tip, when perfect, has four or five straight simple 
hairs, best seen ina soft specimen. At the upper or distal end of each segment there are 
one or two short hairs. Around the basal segment are numerous hairs with lateral spikes. 
Lesser or Internal Antenne (Pl. XIX. fig. 14).—On the hollow basal swelling a ridge 
of somewhat short hairs runs along the external or ventral surface, a little behind the 
prominent anterior margin of the part. They are of various kinds, smooth, spiked, and 
serrated at the tips, many being both spiked and serrated. They have parasitic growths, 
but less conspicuously than the foregoing. At the base of the limb of this organ, on the 
inner or dorsal edge of the ridge or socket, there is a tuft of short hairs, spiked in the 
usual manner. The long segments of the limb are quite bare, except at the origin of the 
two small appendages, where there are a few short simple hairs. The hairs on the larger 
of the two little jointed appendages at the extremity of the organ begin a little above its 
base, on the concave side of the curve, and extend to the fourth segment from the tip, 
only a few simple ones occurring at the distal end of the last three segments. The 
former take their origin in rows from about half the breadth of each segment of the 
appendage, and are pale and translucent ; even a number pressed together do not darken 
the field of the microscope. They are of a beautifully jointed structure, not unlike a 
single filament of an Alga, and are essentially different from an imbricated hair, such 
as the sheep’s, both in the appearance of the other parts and in the nature of the trans- 
verse markings. The tip in some cases is very slightly serrated, and not much tapered. 
In many the delicately serrated tip appears to have suffered abrasion, for only faint 
markings are visible. When viewed with the naked eye or with a pocket lens, they 
present a lustrous golden hue. In Crabs which have recently cast their shells they are 
found still paler; some, as in the former case, having distinct notchings at the tip, 
others without them. It would thus seem that the latter is quite as normal a condition 
as the former, since no abrasion could have affected these under such circumstances. 
The tip of this appendage has a tuft of three or more long, delicate, and smooth hairs. 
The segments of the smaller appendage have a few short bristles at the distal end of each, 
arranged in a very regular manner. At the end of the last segment there is a tuft of 
very short and delicately set hairs. 
aes Ss an of the parts of the internal antenne supplied with hairs, especially 
bodie ee e joints of ‘the larger terminal appendage, is well shown in the 
— animal hen the organ is irritated and the results are compared with a like 
irritation of other parts, and even of the external antennae. When the latter are pulled 
