ZOOPHYTES. 



15 



no radiated structure was externally apparent. In the present 

 class, It begins to be manifested, not in the form of the body 

 but in the arrangement of the parts surrounding the mouth.' 

 Ihese organs or tentaada, being capable of considerable 

 distension, and being used for the capture of food, probably 

 suggested to the Greek naturalists the application to the 

 animals of the word -poI>/pi,^^ the same which they applied 

 to the many-armed Cuttle-fishes, to which externally they 

 bear some resemblance. "^ 



The Zoophytes or Polypes, for by both of these terms are 

 they st.ll designated, may be arranged in four great divisions, 

 to each of which m turu our attention may be briefly directed 



Order I.— IIYDROIDA.* 



In the first family {Hjjdrmdm) of the present order, is found 



the common fresh-water Hydra {Fig. 7), a singular beinc, 



whose history is more strange than the strangest fairy tale 



Iwo species are abundant in » j . 



pools and ditches during warm 



weather; one {H. fnsca), fur- 



nished with tentacula capable 



of being distended many times 



the length of its body; the 



other {H. viridt's), with a shorter 



tentacula, and of a greenish 



colour. Seen in its contracted 



state, on the lower side of a 

 leaf or a twig, floating on the 

 water, it appears a little piece 

 of jelly, not larger than the 

 half of a pea. By extending 

 and contracting its body, it can 

 move along, and change its 

 place at pleasure, executing Fig. 7.-Hydra8. 



a variety of movements not unlike those of the Caterpillars 

 hereafter mentioned as the "geometric. " When it is engaged 

 m taking food, its favourite position seems to be the vertical, 

 which 13 maintained by a singular proceeding. The tail, or 

 * The terra means "Hydra-like." 



