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CHAPTER IX. 

 FILARIID^. 



THE Filariida 1 present the simplest structure of any 

 nemathelminths, and those parasitic in man are, there- 

 fore, considered before the other nematodes. In most 

 cases they have a complete intestinal canal, The mouth 

 is terminal and unarmed, though in some species papillae 

 are found near it. The oesophagus is moderately mus- 

 cular, presents no dilatations, and passes into an alimen- 

 tary canal of practically the same calibre. The anus 

 is sub-terminal in both sexes. 



The opening of the female genital organs, the genital 

 pore, is near the head and sometimes close to the mouth. 

 From the genital pore a short muscular vagina leads into 

 a dilated thinner-walled portion, and into this the two 

 uterine tubes open. These tubes run directly backwards 

 parallel to each other and end in the solid ovaries, which 

 are somewhat convoluted and form loops towards the 

 caudal extremity. 



In the male the testis (single, as in all the Nematoda) 

 commences towards the head end as a loop, and the vas 

 deferens runs directly backwards to open at the cloaca. 

 From the cloaca are extruded two unequal spicules, of 

 which the larger is anterior and often appears to be 

 tubular. These spicules can be protruded or retracted 

 independently of each other. Sensory papillae occur in 

 pairs before and behind the cloaca, but may be so small as 

 to easily escape observation. There are one or two post- 

 anal pairs, and three pre-anal. The males are smaller, often 



1 Termed Filaridce by some authors. 



