492 



PENTASTOMIDA 



Pentastoniids are bisexual. The males are as a rule much 

 less numerous and considerably smaller than the females, although 

 the number of annuli may be greater. 



The ovary consists of a single tube closed behind. This is 

 supported by a median mesentery. Anteriorly the ovary passes 

 into a right and left oviduct, which, traversing the large hook- 

 gland, encircle the alimentary canal and the two posterior nerves 

 (Fig. 258). They then unite, and at their point of union they 

 receive the ducts of the two spermathecae, usually found packed 

 with spermatozoa. Having received the orifices of the sperma- 

 theca, the united oviducts are continued backward as the uterus, 

 a highly -coiled tube in which the fertilised eggs are stored. 

 These are very numerous ; Leuckart estimated that a single female 



Fig. 258, — Diagrammatic represeutatioii of the alimentary, secretory, nervous, and repro- 

 ductive systems of a female Porocephalus teretiusctUus, seen from tlie side. Tlie 

 nerves are represented by solid black lines. (From W. Baldwin Spencer.) 



1, Head-gland; 2, oviduct; 3, ' hook-gland ; 4, mid-gut; 5, ovary; 6, hind-gut; 7, 

 vagina.; 8, uterus; 9, accessory gland ; 10, s])ermathcca. 



may contain half a million eggs. The uterus opens to the 

 exterior in the mid-ventral line a short distance — in F. tereiius- 

 culus on the last ring but seven — in front of the terminal anus. 

 In L. taenioides the eggs begin to be laid in the mucus of the 

 nose some six months after the parasite has taken up its 

 position. 



The testis is a single tube occupying in the male a position 

 similar to that of the ovary in the female. Anteriorly it opens 

 into two vesiculae seminales, which, like the oviducts, pierce the 

 hook-glands and encircle the alimentary canal (Fig. 257). Each 

 vesicula passes into a vas deferens with a cuticular lining. 

 Each vas deferens also receives the orifice of a muscular caecal 

 ejaculatory duct, which, crowded with mature spermatozoa, 

 stretches back through the body. Anteriorly tlie vas deferens 

 passes into a cirrus-bulb, which is joined by a cirrus-sac on one 

 side and a dilator-rod sac on the other, structures containing 



