NO. 1404. PARASITIC COPEPODS—fALIGID.E— WILSON. 519 



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

 segments in which thej are situated. 



The combined action of all these muscles produces a latcMal motion 

 of the posterior seoments of the body, Hexion, 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 



Fig. 25. — MrsruLATURE of a male Homoiotes palliata. a. flexors of front.vl plates; b, e. d, 



MU.SCLES PRODUCING FLEXION BETWEEN THE CEPHALON AND THORAX; 0, EXTENSORS OF FREE SEG- 

 MENT, GENITAL SEGMENT AND ABDOMEN; f, EXTENSORS BETWEEN THE GENITAL SEGMENT AND ABDO- 

 MEN; g-, PRODI'CE FLEXION BETWEEN THORACIC AND LATERAL AREAS; h, i, MOTOR MUSCLES OF THE 

 SECOND AND 7HIRD LF/JS; j, ELEVATORS OF THE MOUTH TUBE; k, MOTOR MUSCLES OF MOUTH TUBE; 

 1, MANDIBLE MOTORS: 111, MOTORS OF SECOND MAXILL.E. 



numl)er of nuiscles, some extending forward, others backward, and 

 still 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 nuiscles which ai'ches or depresses the carapace, and 

 which makes of it an organ of pn^hension in the foi-ni of a large, suck- 



