VI 



ABA CHNOIDEA0 UTER OBGANISA TION 



511 



way through the enteric wall and enter the liver or lungs. They here become 

 encysted and undergo a remarkable metamorphosis, passing through many moults : 

 the final result is a larva which has been named Pcntastoma denticulatum. This larva 

 finally breaks through its cyst and moves about. If it in any way (most often with 

 the flesh of its host) reaches the mouth and throat of the definitive host, it chooses 

 its future place of location, and through a series of moults develops into the adult 

 Pcntastomum. 



I. Outer Organisation. 



A. The Body. 



If we compare the body of the Arachnoidea with that of the 

 Antennatu, the most important difference that strikes us is that in the 



Fig. 35S. Galeodes Dastuguei 9 > natural size. 1-0, The six pairs of extremities ; 1, chelicerse 

 2, pedipalps ; c, head ; th, the thorax of 3 segments ; ab, the abdomen (after L. Dufour). 



former no head distinctly marked off from the thorax, or, what is the 

 same thing, on thorax separated from the head, can be distinguished. 



