60 
COMPARATIVE ZOOLOGY. 
eola ): a, antennae; m, 
mandibles; mx, max¬ 
illae; mp, maxillary 
palpi; lb, labrum; l, 
labium, or tongue. 
As most of the Arachnids live by sue- 
tion, the jaws are seldom used for masti¬ 
cation. In the Scorpion, the apparent 
representatives of the mandibles of an 
Insect are transformed into a pair of 
small forceps, and the palpi, so small in 
Insects, are developed into formidable 
claws: both of these organs are prehen- 
sile. In Spiders, the so-called mandi¬ 
bles, which move more or less vertically, 
end in a fang; and the club-like palpi, 
often resembling legs, have 
nothing to do with inges¬ 
tion or locomotion. Both 
Scorpions and Spiders have 
a soft upper lip, and a 
groove within the mouth, 
which serves as a canal 
while sucking their prey. 
The tongue is external, and 
situated between a pair of 
diminutive maxillae. 
In the Ascidians the first 
part of the alimentary canal 
is enormously enlarged and 
modified to serve as a gill- 
sac. At the bottom of this 
sac, and far removed from 
its external opening, lies 
the entrance to the diges¬ 
tive tract proper. Into it 
the particles of food enter- F.G. 25,-Under Surface of Male Spider: a, 
ine: with the water are con- c ’ P ois,on -fa n g; teeth on interior mar- 
J /T-I* _ , gin of mandible, e; f, labium; g, thorax; 
veyed (lig. 279). ti, limbs; i, abdomen; l , spinnerets; m, 
The mouth of Yerte- JTf” 7 palp " s; * di,ated 
