APPENDIX TO ARACHNIDA 303 



which is supposed to be hsemolytic, open at the bases of the 

 hooks. 



The gut passes straight through the body to the terminal 

 or subterminal anus. The reproductive glands fill the rest of 

 the body-cavity with their coils ; they open in the male a 

 short way behind the mouth, in the female just in front of the 

 anus. The male as a rule is smaller than the female. 



The eggs, which are produced in myriads, are passed 

 from the body of the parent's host either by the nose or 

 mouth, or in the faeces. Being of microscopic size they are 

 blown about like the dust when once they get free. Most of 

 them must perish, but some of them getting among herbage 

 or into water will be swallowed, and thus may reach a hos- 

 pitable stomach, where the young can develop. 



The minute larva has two pairs of stumpy appendages 

 ending in hooks, and also some anterior chitinous spicules 

 with which it burrows into the wall of its host's stomach, or 

 bores right through the wall and reaches some more vascular 

 organ — commonly the spleen or liver — where it becomes 

 encysted. Sometimes larvae may wander into some vital 

 part, like the brain, and may cause the death of the host. 

 But in ordinary circumstances the encysted larva remains 

 quiet, growing and moulting, until it becomes a good deal 

 like the parent in form. If at length the host in which the 

 full-grown larvae are encysted (intermediate host) be eaten by 

 some carnivorous animal, the larvae may happen upon a 

 second hospitable stomach, from which they may find their 

 way into the nasal passages or lungs, where they attach 

 themselves and become adult in this their final host. 



Both as adults and as encysted larvae Pentastomida have 

 occasionally been found in man. 



Three genera are at present recognised, and are all 

 included in a single family, LinguatulidcB. 



Genus i : Linguatula. Body flat, tapering behind, almost 

 like certain species of flukes, finely ringed like a leech. The 

 adult lives in the nasal sinuses of its host. Both larva and 

 adult have been found in many parts of the world in numer- 

 ous species of animals, including rabbit, ox, pig, and horse 

 (larva) and dog, sheep, horse, and man (adult). 



Genus 2: Porocephalus (Fig. 133). Body cylindrical, 



