CORNISH FAUNA. 



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CORNISH ZOOPHYTES. 



SUB CLASS I. 



RADIATED ZOOPHYTES. 



Body contractile in every part, symmetrical; mouth sBid 

 anus one; geniniiparous and oviparous. 



ORDER I. 



HYDROIDA. 



This, the first order of Zooyhytes, is very commonly dis- 

 tributed on all parts of our coast from the tide marks to 

 mid-channel; and the individual speries are of such delicate 

 and elegant shapes, as seem pecuh'arly fitted to invite 

 attention and study. The outward forms vary from a single 

 stem to the bushy appearance of the Ostrich feather or the 

 Squirrel's tail ; and the examination of their n)inute structure 

 and economy shows an equal variation which adds g^reatly to 

 the pleasure of their study. The arrangement followed in 

 this essay, is based on the character of the animal or polyps 

 and is in some measure independent of the form and character 

 of the hard parts or polypidom. Its character is : " Polypes 

 compound, rarely single and naked, the month encircled iviik 

 ronghish Jjliform tentacula ; stomach ivithout proper parietes : 

 intestine none J anus none ; reproductive gemmules pnliuluting 

 from the body, and naked or contained in external vesicles. 

 Polypidonts horny, fistnlar, more or less phytoidal, fixed, ex- 

 ternal." When the polypidom is present, it is always 

 external and horny ; but there are several species belonging 

 to it which have none; and these are called Naked liydroidu. 

 Of the naked species, which inhabit fresh water, I have 

 hitherto found none in Cornwall; though probably a more 

 extended search may be successful, as the Hydra viridis has 

 been found in Devon by Turton. 



It was on these naked creaUires that Trembly made his 

 reniaikablc espeiiments, by which it was proved that they 



A 



