THE ANxVTOMY OF PENTASTOMDM TERETIUSCULUM. 49 



of the wall will, by their rhythmic contraction, ensure the 

 passage of the egg to the exterior. Its small calibre, 

 thick cuticular lining, the epithelial and muscular layers, 

 and its straight course distinguish it at once from the 

 coiled thin-walled portion which is crowded with eggs, and 

 serves as a uterus. Possibly it may represent the original 

 vagina of the young form, the uterine portion being an after- 

 growth intercalated between the oviducts and the vagina 

 proper. 



(2) Male. — The organs in the male form consist of the 

 following parts, and are more complex than those of the 

 female : 



(«) Testis. 



(b) Vesiculse seminales. 



(c) Vasa deferentia. 

 {d) Ejaculatory duct, 

 (e) Cirrus bulb. 



(/) Dilator rod sac. 



(g) Cirrus sac. 



{h) Atrium genitale. 



(a) Testis. — This has the form, as in P. proboscideum^ 

 and P. protelis,^ of a single median tube. It lies dorsal to 

 the alimentary canal, and extends for the greater part of the 

 whole length of the body, commencing close to the posterior 

 extremity, and running forwards to a point a little behind the 

 level of the external male opening (fig. 6). 



In the young form the tube has a wall composed of a thin 

 membranous layer externally, and internally a thick multi- 

 cellular layer. In the latter the outlines of the cells cannot 

 be clearly distinguished; possibly it is in reality a syncytium, 

 in which are many small nuclei (fig. 21, T.). 



In the adult the testis is large, and may occupy up to as 

 much as one half of the space in the body-cavity. The interior 

 is crowded with masses of sperm in all stages of development, 

 and mature sperms are to be met with, attached together in the 



1 Stiles, loc. cit., p. 131, Taf. viii, fig. 48. 



2 Hoyle, loc. cit., p. 182, pi. xxviii, figs. G— 8. 



VOL. XXXIV, PART I. NEW SER. D 



