POLYPIFERA. 



17 



Fig. 6. 



24. A branch of red coral is represent- Fi s- 

 ed by Fig. 5, with the little animals at 



work on it. 



25. 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 contract- 

 ed state, as when the branch is removed 

 from the fluid. 



26. 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. 



27. It has been ascertained that these 

 fixed zoophytes are multiplied like the 

 sponge by gemmules, in the manner simi- 

 lar to that already described. 



28. The mechanism by which some species of polypi 

 produce a constant current of water toward their mouths, 

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

 without describing it. 



29. When the tentacula are expanded, small particles 

 in the water may be observed constantly tending toward 

 the mouths of these animals. This motion of the water is 

 not produced by the motion of the tentacula themselves, 

 but is the effect of the rapid vibration of minute cilia placed 

 along their sides. 



30. In the species calledflustra carbacea, the tentacula 

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

 lateral margins of each, there Fig. 7. Fig, 8. 

 is a single row of cilia extend- 

 ing from the base to the ter- 

 mination. . This animal is rep- 

 resented in the posture of 



forming the current by Fig. 7. f/, 



Fig. 8 is a portion of a tenta- 

 cula highly magnified, to show 

 the cilia, and the manner in 

 which the current is produ- 

 ced. From the positions in 



2* 



