514 



COMPARATIVE ANATOMY 



CHAP. 



segmented body has here come from the fusing of an unsegmented 

 cephalo-thorax with an unsegmented abdomen. It only rarely occurs 

 that the limbless abdomen is distinctly marked off from the limb- 



Fig. 361.— Larva of Gamasus rucorum (after Winkler). 1-6, The 6 pairs of extremities of the 

 larva (tlie sixth still wanting); 1, the chelicera^ = mandibles ; 2, the pedipalps = maxillse ; m, 

 muscles ; vm, Malpighian vessels ; g, brain = supra-cesophageal ganglion ; Is, diverticula of the mid- 

 gut (hepatic tubes) ; md, mid-gut ; Ji, heart ; ac, aorta-cephalica ; r, rectal vesicle. 



bearing cephalo-thorax. An anterior portion of the body, often 

 distinguished as the "head," and carrying the oral aperture, can 

 certainly not be regarded as an original division of the body, i.e. a 



