SECT. in. ZOOPHYTES. Si 



SECTION m. 



HYDROZOA, ZOOPHYTES. 



ZOOPHYTES are animals of a much higher organization 

 than the Protozoa, inasmuch as they are furnished 

 with special organs of prehension, offence and defence, 

 of attachment, and in many of locomotion. For the 

 most part they consist of numerous individuals called 

 Polypes, united in a community, and living together in 

 intimate sympathy and combined action, so as to form 

 one single compound animal. 



Zoophytes are divided into two groups, namely the 

 Hydrozoa, whose type is the common fresh- water Hydra, 

 and the Actinozoa, which are composite animals, in- 

 cluding the reef-building corals, whose polypes are 

 formed according to the type of the Actinia, or common 

 Sea Anemone. The Hydrozoa consist of seven orders, 

 the first of which are the Hydridse, inhabitants of fresh 

 water ; the next constitute the oceanic Hydrozoa, some of 

 which, though extremely varied in form, are connected 

 by the most wonderful relations. 



The solitary Hydra that lives in fresh-water pools 

 and ditches, consists of a soft cylindrical muscular bag, 

 capable of being stretched into a slender tube, shrunk 

 into a minute globe, or widely distended at will. At 

 one end there is a circular mouth, which is highly sensi- 

 tive, opening, closing, or protruding like a cone, and 

 surrounded at its base by six long flexible arms called 

 tentacles, arranged symmetrically. The mouth opens 



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