60 



COMPARATIVE ZOOLOGY. 



As most of the Arachnids live by suc- 

 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 



PIG. 24. Mouth of the i i , i / , i i 



H>rj-fly(7'u&aMKn- claws i both of these organs are prehen- 



sile. In Spiders, the so-called mandi- 



eola): a, antennae; m, 

 mandibles; mx, max- 

 illae; mp, maxillary bles, which move more or less vertically, 



' palpi; Ib, labrnm; I, ' J .' 



labium, or tongue. 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- FlG . 25 ._ Ululei . su.-rce or Male Spider: a, 

 ing with the water are con- c > P"""-^; &, <eeth <> interior mar- 



gin of mandible, e; f, labium; g, thorax-, 



(Fig. 279). >*, limbs; <, abdomen; I, spinnerets; m, 



m , -T7- maxillary palpus; d, dilated terminal 



The mouth of Verte- joint. 



