3 20 



MANUAL OF ZOOLOGY. 



" chelicerae," or ch elate mandibles, and with two well- devel- 

 oped maxillary palpi, behind which in the female is a pair of 

 false legs which carry the ova. The abdomen is rudimentary; 

 but the cephalothorax is segmented. Though there are no 

 respiratory organs, there is a distinct heart. The sexes are in 

 different individuals, and the larvae have at first only two pairs 

 of legs. 



ORDER II. ACARINA or MONOMEROSOMATA. The mem- 

 bers of this order possess an unsegmented abdomen which is 

 fused with the cephalothorax into a single mass. Respiration 

 is effected by trachea, or by the integument. Most of the 

 Acarina are parasitic, and the most familiar are the Mites 

 and Ticks. 



Family i. Pentastomida {Linguatulince). The members of 

 this family are worm-like parasites, which in their adult state 

 are found in the interior of the frontal sinuses, the nose, or the 

 lungs of the Dog, and of other Vertebrate animals. When 

 fully grown (fig. 163) they are completely vermiform, with a 



soft annulated integument, and pos- 

 sessing no external organs except 

 two pairs of retractile hooks, re- 

 presenting limbs, placed near the 

 mouth. The adult thus presents 

 an external resemblance to the 

 Tcznia, from which, however, they 

 are separated by the details of their 

 internal organisation. There are 

 no differentiated organs of respira- 

 tion or circulation, but the sexes 

 are distinct. The larvae (fig. 163, 

 B) are found encysted in the liver 

 or other internal organs of various 

 Vertebrates (including man), and 

 possess two pairs of articulated 

 limbs. 



Family 2. Tardigrada (Macro- 

 . ., biotida or Arctisca\ This family 



Fig. 163. A, Pentastoma t&motaes, . / * 



female, of the natural size; C, Male COmpriSCS the SO-Called blOth Or 

 of the same, of the natural size ; B, (t T> A t-iirYiol^nl^o " \nrViirVi orp TYII 

 Larva of the same, greatly enlarged, -bear AnimalCUlCS, WftlCn are mi- 

 showing the two pairs of articulated croscopic animals found in damp 

 oss and in the gutters of houses 

 (fig. 165, B). In form, the body is 

 somewhat vermiform, with four pairs of rudimentary legs. The 

 mouth is suctorial, with rudimentary jaws or stylets. They 

 exhibit no traces of respiratory or circulatory organs, and, un- 



