558 CLASS 1X. 
The feet or legs of arachnids do not present exactly the same 
typus as those of insects. They consist usually of seven joints, and 
are not thinner towards the extremity, so that the tars? differ less 
from the other parts than in insects. If we suppose that the two 
last joints belong to the tarsus, then the tibia consists of two joints 
of which the first in some is the longest (e.g. Scorpio and Phrynus), 
in others the second. The long joint that precedes it is the femur 
which succeeds a short, inversely conical joint corresponding to the 
trochanter i hexapod insects. The first joint, broader, commonly 
inversely conical, by which the feet are attached to the cephalo- 
thorax, corresponds to the hip (coxa) of insects. In Phrynus, the 
tarsus of the fore legs consists of a great number of joints (thirty 
and more), of extraordinary fineness, and in the remaining feet of 
three joints. The last joint of the tarsus has usually two curved 
hooklets, and in some a membranous or vesicular cushion (pulvillus) 
in addition at the under side. What is most distinctive in the com- 
position of the feet in arachnids, is the division of the tibia into 
two pieces. In Phrynus, the tibia of the fore-feet, like the tarsus, 
consists of numerous thin joints; those of the second and third pairs 
of feet of the usual number, two; those of the fourth pair of five, of 
which the first exceeds the rest in length remarkably. 
The cephalothorax often presents a line or groove on each side 
of the simple eyes placed in the middle, indicating an imperfect 
separation, so that the head looks like a wedge or triangle, with the 
point turned backwards, upon the thorax. The upper surface of 
Sc, nat. 2e Série, 1. Zoolog. p. 7, and by Ertcuson, Entomogr. s. 8.] In the scorpions 
there are two horny triangular plates between the first pair of feet, which may be 
regarded as mentum, a part wanting in the rest of the anachnids. An upper lip 
(labrum) is not present in these any more than in the rest. According to this view 
arachnids would have only three pairs of feet, like most insects. Yet Zoology must 
nevertheless still continue to assert that arachnids have four pairs of feet, since, in 
reality, four pairs of jointed appendages of the cephalothoraw do always act as feet. 
Even the jaws of hexapod insects are in a wider sense modified feet. Feet and jaws 
are parts having the same fundamental form. This is proved by the history of develop- 
ment. Both these parts are, according to the investigation of RATHKE in the Cray-fish, 
of the same form, and the dissimilarity between feet and jaws, which is seen in perfect 
cray-fishes, is merely the consequence of subsequent development (Untersuchungen tiber 
die Bildung u. Entwickelung des Flusskrebses, Leipsig, 1829, fol. s. 67, 68). In young 
and still imperfect individuals of Cyclops quadricornis, according to the figures of 
JURINE, the upper jaws and the last pair of under jaws serve for swimming, and have 
much resemblance to the feet which are developed only at a later period. RatTHKE loc. 
cit. p. 73. 
met 
ote. 
