214 



ZOOLOGY. 



the integuments becomes ossified, BO as to form for it a kind 

 of calcareous or horny dwelling (Fig. 167) ; and in most cases 

 also the young spring from granulations arising on the surface 

 of the bodies of their parents, and as they do not become de- 

 tached, constitute animated masses of varied forms, resembling 

 a branching plant loaded with flowers. 



The actiniae or sea-anemones (Fig. 145) belong to this 

 class ; so also does the coral polyp (Figs. 164, 166), the cary- 

 ophillis (Fig. 167), &c. 



Sponges (spongiarise) offer a fourth type; these are sin- 

 gular animals, which, when young, have an ovoid form, 

 swim freely by means of the vibratile cilia with which 



Fig. 167. Polyp of the Genus 

 Caryopnillis. 



Fig. 166. Stalk of the Coral. 



Fig. 168. The Sponge. 



their bodies are provided, and resemble at this stage of their 

 growth the larvae of the acalepha and of the polyps ; but they 

 soon become fixed (Fig. 168), and then lose not only their 



