POLYPIPERA. 



Fig. 6. 



Fig. 5. A branch of red coral is represented 



by fig. 5, with the little animals at work 

 on it. 



Fig. 6 is a part of one of these 

 branches magnified, and showing the 

 tentacula expanded as when the animal 

 is under water ; and also in the con- 

 tracted state, as when the branch is 

 removed from the fluid. 



These structures are fixed perma- 

 nently to stones or rocks at the bottom 

 of the ocean, which in warm climates 

 are often covered with them to a great 

 extent. 



It has been ascertained that these 

 fixed zoophytes are multiplied like the 

 sponge, by gemmules, in the manner 

 similar to that already described. 



The mechanism by which some species of polypi pro- 

 duce a constant current of water towards their mouths 

 is so curious that we should not do justice to this subject 

 without describing it. 



When the tentacula are expanded, small particles in 

 the water may be observed constantly tending towards 

 the mouths of these animals. This motion of the water 

 is not produced by the motion of the tentacula them- 

 selves, but is- the effect of the rapid vibration of minute 

 cilia placed along their sides. 



In the species called Flustra Carbacea, the tentacula 

 in each polype are twenty-two in number, and along the 



Fig. 7. 



Fig. 8. lateral margins of each, there 

 is a single row of cilia extend- 

 ing from the base to the ter- 

 mination. This animal is re- 

 presented in the posture of 

 forming the current by fig. 7. 

 Fig. 8 is a portion of a tenta- 

 cula highly magnified, to show 

 the cilia, and the manner in 

 which the current is produc- 

 ed. From the positions in 

 which the cilia stand, it will be observed that their mo- 



