PRIMARY DIVISIONS AND CLASSES. 



225 



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. 168) belong to this 

 class ; so also does the coral polyp (Figs. 187, 189), the cary- 

 ophyllia (Fig. 190), &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 their 

 bodies are provided, and resemble at this stage of their 



Fig. 190. Polyp of Ihe Genus 

 Caryophyllia. A Coral Polyp. 



Fig. 189. Stalk of the Coral. Fig. 191. The Sponge. 



growth the larvse of the acalephae and of the polyps : but they 

 soon become fixed (Fig. 191), and then lose not only their 

 sensibility and power of motion, but become so degraded as 

 to resemble nothing in the animal kingdom. 



Finally, most naturalists also arrange in the division 



