2S4 



ccelhel:mixthes 



oriL;in of these vessels from the calom the followhig points are in favor, (i) 

 The \"entral eord is enclosed in the \"entrai blood sinus; (^j) the llagellale funnels, 

 just alluded to, lie in the blood laeun;e. ustially in ampullar spaces between the 

 ventral and lateral blood sinuses. Further relations are shown by Aiaulliolhicila 

 ptii'Jiiij. parasitic on fishes. This has both blood-vessels of the oliL;och:rtcs, a 

 bodv cavity di\ided by septa, and cha'ta-. On tlie other hand, it is leechlike 

 in other features; two suckers and se.xual apparatus on the Hirudinean piattern. 

 Braiu-iiiobJcUa, parasitic on the gills of the cravfish, is a cha"'topod devoid of 

 bristles and furnished with a sucker in correlation with its habits. 



Order I. Gnathobdellidse. 



The ja^yed leeches include Hiriido iiicdicinaUs, once extensivelv used for 

 blooddetting, now little employed. Ha-madipsa includes land leeches of the 

 tropics. KcpJicUs* soft jaws. MacyobdcUa''* includes oitr largest species. 



Order II. Rhynchobdellidffi. 



\A'lthout jaws. Clepspixid.e mostlv feed on snails and fishes. Clcpsinc* 

 Hirmcnlaria ghilijiii of South America is poisonous. Ichthyobdellid.e,* 

 cylindrical, occur in salt and fresh water, parasitic on fishes. Ichthyobdella,* 

 Ponlohdi'lla,'" marine; Piscicola, fresh water. 



Class IV. Polyzoa (Bryozoa). 



In external appearance the Polyzoa closely resemble the hydroids, 

 so diat the inexperienced have dilticulty in distiti- 

 guishing them. Like them by budding thev form 

 colotiies which are either incrusting sheets or assume 

 a more bush-hke character. Further they have a 

 crown of ciliated tentacles which can be spread out 

 or quickly retracted. In internal characters tlie two 

 groups are greatly difierent. The Polyzoa ha^•e a 

 complete aUmentary canal, with its three divisions, 

 wliich is bent upon itself so that the anus has near 

 the mouth. The central ner^•ous s}'stem lies be- 

 tween mouth and anus, and the single pair of nephri- 

 dia empty by a common opening. Bevond tliis it is 

 dilhcult to go, since tlie two groups — Fjttoprocta 

 and Ectoprocta — differ wddely. The Ihitoprocta 

 have no cadom, resembling in this respect the 

 Rotifera; the Ectoprocta are true Cadhelminthcs 

 and by way of Flionvtls show resemblances to the 

 Sipunculoida ('Prosopygii,' p. 2S1) and also to the 

 Annelida. 



Fig. J73. — Loxoso}ihi 

 sliigulare (after Nit- 

 sche) in optical sec- 

 tion. .1, rectum; Ca, 

 ganglion; J. intes- 

 tine; T, tentacles; l', 

 stomach. 



Sub Class I. Enloprocta. 



The single intlividuals of the Entoprocta (fig. 273) arc shaped like a wine- 

 glass and are p)laced on stalks which rise from (usually) creeping stolons. The 



