Pentastomida. 
117 
APPENDIX TO ARACHNIDA. 
PENTASTOMIDA. 
The Pentastomida, or Linguatulida, represented in Wall- 
case 7 by Pentastomum armillatum from an African python, 
and Linguatula taenioides 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 the 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- 
branes of a mammal, forms an interesting link in the life-history 
Fig. 80. 
Pentastomum armillatum. (Natural size.) 
of these creatures; it appears that the python gets its lung- 
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 are 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. 
Wall-case 
No. 7. 
