no. 3404. PARASITIC CQPEPODS—CALlGIBM-WILSON. 519 



abdomen (f). These of course produce flexion between the two 

 segments in which they are situated. 



The combined action of all these muscles produces a lateral motion 

 of the posterior segments of the body, flexion, extension, or a telescopic 

 contraction of the different body regions. In addition to these muscles 

 the thoracic area on either side of the mid line is provided with a 



Pig. 25.— Musculature of a male Homoiotes palliata. a. flexors of frontal plates; b, c, d, 



HI -i I IN PRODUCING FLEXION BETWEEN THE CEPHALON AND THORAX; (.', EXTENSORS OF FREE SEG- 

 MENT, GENITAL SEGMENT AND ABDOMEN; !'. EXTENSORS BETWEEN THE GENITAL SEGMENT AND ABDO- 

 MJEN; g, PRODI CE FLEXION BETWEEN THORACIC AND LATERAL AREAS; 1). i, MOTOR MUSCLES OF THE 

 -mom, ami HIRD LEGS; j, ELEVATORS OF THE MOUTH TUBE; k, MOTOB MUSCLES OF MOUTH TUBE: 

 1, MANDIBLE MOTORS; in. MOTORS OF SECOND MAXILL.K 



number of muscles, some extending forward, others backward, and 

 si ill others laterally. A few of these are for producing flexion between 

 the thoracic and lateral areas and assisting the three pairs already 

 described in flexing the thorax on the cephalon (g). It is the combined 



action of these muscles whieh arehes or depresses the carapace, and 

 which makes of it an organ of prehension in the form of a large, suck- 



