60 



COMPARATIVE ZOOLOGY. 



Fia. 24. —Mouth of the 

 Horse-fly (Taharma lim,- 

 eola) : a, auteunffi ; m, 

 mandihles ; mrr, max- 



As most of the Araelinids live by suc- 

 tion, the jaws are seldom used foi* 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 tliese organs are prehen- 

 sile. In Spiders, the so-called mandi- 

 iiiffi; mp, maxillary bles, which move morc or less vertically, 



palpi; lb, labrumj I, \ i , vi . i • 



labiam, or tongue. end in a tang; and the clnb-hke 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- w,„ ,« tt ., c . 



., , ^"G-26.-Uncler Surface of Male Spider: o, 



ing With the water are con- "' poison-faug j &, teeth on interior mar- 

 VPved CFio- 9'7q\ gmof mandible e; /, labium; g, thorax; 



Veyea {t!\g. ^^y). ?., l,mbs; i, abdomen; ;, spinnerets; m, 



The mouth of Yerte- S!'""'' '""""'= '' ^'""'^ ''™'"'" 



