ACANTHOCEPHALA 



343 



Thence a peculiarly constructed apparatus finally conveys the eggs out. 

 This apparatus consists of the uterine bell and vagina ; the latter dis- 

 charging at the posterior extremity of the body. The belJ is a muscular 



canal provided with apertures at both the anterior 

 and posterior extremities. Its interior space is 

 in direct communication with the body cavity, 

 and the anterior orifice takes up all material 

 floating in the cavity egg-balls, mature and im- 

 mature eggs and pushes these further back- 

 wards. The continuation of the bell-lumen is 

 now narrowed by a number of large cells in 

 such a manner that only bodies of a certain 

 form can pass through this tract and attain the 

 uterus ; everything else is conveyed back into 

 the body cavity through the posterior opening 

 of the bell. 



The eggs are already fertilised in the body 

 cavity, and in this locality go through their de- 

 velopment to the formation of the embryo. 

 Completely developed eggs are surrounded by 

 three shells, and are generally fusiform. The 

 eggs agglomerate in masses in the uterus until 

 they are finally deposited through the vagina 

 and vulva. For the further development, the 



R.r. 



FIG. 223. The male of 

 Echinorhynchus angustatus. 

 25/1. L., lemnisci ; T., tes- 



FIG. 224. Anterior portion of the female apparatus 

 of Echinorhynchus acus (magnified). (After Wagener.) 



tides ; P., prostatic glands ; On the left seen from behind, on the right seen 



Pr., sheath of proboscis, with from the front. F., Inferior orifice of the bell; B., 



ganglion; R.r., retractor of bell ; Lig., ligament; M., mouth of bell ; Ut., uterus, 

 sheath of proboscis. 



transmission of the eggs into an intermediary host, usually a crustacean 

 or an insect, is necessary ; the metamorphosis is very complicated ; but 

 this transmission may be very easily effected artificially by feeding suitable 

 crustaceans (asellus, gammarus, &c.) with the eggs of acanthocephala ; this 

 being the only method of inducing the larva to hatch out so that its 



