288 THE MECHANICAL FUNCTIONS. 



or thigh, F ; two portions of the leg, L ; and 

 the tarsus, p. The haunch is usually short, 

 being interposed merely as a base for increasing 

 the extent of motion of the pieces which follow : 

 and sometimes it is itself composed of more than 

 one piece. The leg is usually divided into two 

 pieces, by a joint. The tarsus is terminated by 

 a single or double hook, and sometimes by a 

 pincer, or claw r . 



New organs, not met with among the Arach- 

 nida, are here for the first time developed, 

 namely, the Antenna, of which there is one on 

 each side of the head. They are denominated, 

 in popular language, the feelers; although it is 

 more than probable that they perform some 

 function of higher importance than that of con- 

 veying perceptions of mere touch. The antenna? 

 consist of slender filaments, composed of a great 

 number of pieces articulated together : and they 

 are infinitely diversified in their form in the 

 different genera and species, both of Crustacea 

 and of Insects. 



The jaws, and other parts connected with the 

 mouth, present a great complication of structure; 

 and many of these parts are employed in various 

 uses besides those of mastication ; such as the 

 seizing of objects, and turning them in various 

 ways for examination ; and, according to their 

 suitableness as articles of food, conveying them 

 into the mouth. These organs are called the 



