Pcutastoniida. 117 



APPENDIX TO AEACHNIDA. 



PENTASTOMIDA. 



The Pentastomida, or Linf^uatulida, represented in Wall- Wall-Ccase 



case 7 by Pcntastomum arviiUatam from an African python, 

 and Linguatuhi lacniuitlcs from the nose of the dog, are always 

 parasitic, and have been so much modified by this habit that 

 there is little left to show their affinity to tlie Arachnida. The 

 segmentation of the body, and the hooks on either side of the 

 mouth, are the sole external indications of their relationships. 

 The third preparation, showing the young in the visceral mem- 

 liranes of a mannnal, forms an interesting link in the life-history 



No. 



Fig. 80. 

 Pentastomnvi armilUttiim. (Natural size.) 



of these creatures ; it appears that the python gets its lun^'^''- 

 parasite from eating a small mammal ; the parasite becomes 

 sexually mature in the lung of its new host, and the eggs from 

 the lung are coughed out, and ai'e taken up by the mammal, 

 when in search of food. 



The external ringing of the body does not correspond with any 

 internal segmentation ; the characteristic hooks are capable of 

 protrusion and retraction ; the only sense-organs are some paired 

 papillae on the head ; the sexes are separate, and the eggs are 

 considerably developed before they are laid. 



