322 



CfELHELMINTIIES. 



open. The space between the horseshoe- shaped intestine and the 

 body surface is completely filled by a pa- 

 renchyma containing muscle cells, and 

 correspondingly the excretory organs are 

 protonephridia. In our fresh-water Urna- 

 tilla gracili.^ * these organs are branched 

 and begin with flame cells. Pedicellina'-'- 

 and Loxosoma, marine. 



Sub Class J I. Edoproda. 



In the Ectoproeta there is a spacious, 

 often ciliated, ccelom between the alimen- 

 tary canal and skin, so that these are 

 separated and have a certain amount of 

 independence (fig. 205). On this account 



Fig. 294. — Lnxo.'^oma ^inqulare. i . -,- ii i / i ii 



(After Nitsche ) Single in- has arisen a peculiar metnocl (wiiollv 

 A";lTtu^^^t"1S*?o°n; indefensible morphologically) of treating 

 stomaeh!""'^'"'"*'"'^''"' ""'them as two individuals, 2»Zi/;j((^, the in- 

 testine and tentacles; cyst id the rest, especially the body wall and 

 skeleton. 



Fro. 295.— J^/u.s^rrt membranacpa (.ifter Nitsche"), a single animal, o. anus; ri;, ectocyst: 

 en, entocyst; /, funiculus; ,(/, t^antxlion; A-, collar wliich i>rrniits complete retrac- 

 tion; Tji, stomach, also lierinai muscular sac; o, (.ij-sophat^us. .1, avicularium; /?, 

 vibracularilim of i?f(,f7((/(i. (.^ftcr (Mai)ari>de.i 



The cystid is cup-shaped or saccular. It consists of an cndo- 

 cyst — the body wall — and an ectocyst — a cuticular skeleton, usually 

 strongly calcified, secreted by the ectoderm. The surface of the 



