120 BRITISH TYROGLYPHJD7E. 



4. The muscles of the alimentary canal. 



5. The muscles of the genital system. 



6. The muscles of the legs. 



The Muscles of the Rostrum and Mandibles. 



The greater portion of the open space lying above 

 the brain and the anterior part of the ventriculus and 

 below the dorsal integuments of the anterior part of 

 the body, is occupied by two great systems of longi- 

 tudinal muscles, which seem at first sight to con- 

 stitute one system only ; they are both spread out in 

 an almost parallel but slightly converging manner. 

 These muscles all arise from the under (inner) side of the 

 dorsal cuticle, and run forward and downward. Each 

 system consists of numerous bundles which terminate 

 in short tendons ; all, or many, of these tendons unite 

 and form a single large tendon by which they are 

 inserted into the part they move ; such of these 

 muscles as fall in or very near the median line are 

 shown in PL C, fig. ] , which is Hericia Robini ; they 

 of course vary in different species, but the general 

 arrangement is very similar in the species the anatomy 

 of which I am acquainted with. The anterior of these 

 systems is that of the retractor muscles of the mandibles 

 (mdr) ; the furthest forward of which arises from a little 

 behind the rostrum, and the most backward from above 

 about the centre of the supra-oesophageal ganglion. 

 Nalepa says that in Carpogly pJms anonymus they arise 

 from about over the coxae of the second pair of legs. 

 Their tendons are inserted into the hind edges of the 

 mandibles, usually nearer to their dorsal than to their 

 ventral surface : they are large and vigorous muscles, 

 and serve to withdraw the mandibles when they have 

 been protruded : the action is powerful, but the dis- 

 tance that the mandible can be withdrawn is short; 

 very different from the long distance which these 

 organs can be retracted in many Gamasidaa, where the 

 retractors of the mandibles arise almost from the 



