77 



below the liooks. Tlic Krst row of 

 spines is deficient iuferiorly. 



Hookless or orifice end. — Opening Hookless or orifice end. — Opening 

 oblong. Its cavity black throughout, an almost circular cavity, black only 

 Its lips transversely bifid and the in two latei'al sjjots, upper lip semi- 

 lower one much larger than the circular and with four well marked 

 upper. The upper one continuous angles, lower bifid, consisting of a 

 laterally with the side lobes. The tuberous part elongated transversely 

 last segments are arranged telescopi- and also of two bifid protuberances 

 chilly and bear no apjireciable spine- each bearing a mammillury process, 

 lets. There arc spinclcts on tiietwo latter 



and on the lower lij>. The general 

 aspect of the opening is upward. 

 Last segment irregularly telescopic. 



The characters amply prove that the camel hot serves as a 

 connecting- link between the peculiar tough horse bot and 

 ordinary maggots. They show that the strange leather}'- spines of 

 the horse bot are not chitinous or horny nails but true papillae, 

 they show that these papillae tend to arrange themselves in 

 groups and some develop into foot-like organs while the others 

 lose their importance. By contrast of these organisms with com- 

 mon maggots we may infer what features of structure are 

 necessary for a grub that lives in the stomach (as the horse bot 

 does) and what for a resident in the phai*ynx (as the camel bot). 

 The latter, it will be noticed, is softer and less irritant than the 

 former and probably, as having rudimentary false legs, a much 

 better traveller. He makes his exit from the body through the 

 nose, whereas the stomach bot of the horse passes through the 

 anus. The diflEerence in position of the hooks is interesting; the 

 camel parasite has them arranged like a pair of delicate anchors, 

 which he can throw down when he wishes to ob tain a grip 

 sufl&cing to prevent his being swallowed with food, whereas 

 the horse parasite has much stronger grappling hooks arranged 

 like the horns of a stag beetle and suited to enable him to hold 

 tight in whatever direction the churning motion of the stomach 

 may drag him. 



The posterior orifice-like cavity is considered a respiratory sac, 

 but what the black materinl in it is I am not prepared to state. 

 Why does the camel parasite have stalked eyes and the horse 



