1110 



]\vki;tkhi',atk animals. 



united toLjether by a wull-developed nervous sy.steni, and are tlma 

 brought into organic connection witli one another. 



The vast majority of tlie I'ljly^oa are fi.xed, and thus assume a 

 very plant-like appearance. There is one fresh-water type, how- 

 ever (viz., Cristiitdla), in whicli the colony can creep al:iout upon a 

 flattened base very like the fcjot of a slug. In tliis same form, also, 

 alone of all the PoIijziki, there is not any outer covering or ectocyst 

 to the poly|jides. 



The l-'iili/zou are paitly inhabitants of the sea and partly of fresh 

 water, ami they are tlms iii\'iiled into two groups which, as a 



;. l.'!:;.-l. Fra^'iiiriil, ,,f Fhi^,-,, Irtuiml,,, ,„„■ nl' tlic Si':i-iiiii(>i. iialiiviil size. 2. A 



silJ'4lr |„,ly|ililr (.I' I'lilkcrln, iu:i;jiiirn.il, slHiwili;.^ (I iiTllliu' rmwil (if tc-utlicles. 3. 



A |«i|.\-].iiir or Lophnpii:! r nj^tu 1 1 :„ HI, a IVrsl I- wal r r P( ilyzc HI, lli-lllv 111,11,'llilieil, 



sliiiwiii;.' I lie li.iis,-sl sliaii-il nnwn ,,r imtiH-Irs: a Tciiticular crown ; ), Oullrt; 



'■ SIf.ijiiicl, ; J Iiitrstiiir ; .■AuHs; ;/ ( iiz^aiil ; ;, EiMlcicvft; / Ect.ipyst. 



general ruli;, dilfcr from one another considerably in anatomical 

 structure. In niost of the flesh-water I'hIiizok tlie tentacles are 

 b jrne U|ii.n a cri'scentii' disc or stage (tig. \'.VA, 3), so that the crown 

 of tentacles assumes tlie sha])e of a horse-shoe. In almost all the 

 marine foi'ms, on the other hand, the tentacles (tig. 1.3.3, 21 are 

 simply arranged in a ciicle. 



All the I'dIiiz'iii are hcrmaphroilite, each polypide being furnished 

 with tin- Ti'proiliii-tive org.-ins proper to the t\\'o sexes. The eggs 

 are siiii|ily hbei'a.ted int:) the pei'i visceral cavity, where they are 



