232 



GENERAL ZOOLOGY 



Each zooid is microscopic in size, but, as in the rotifers, 

 we can identify definite and rather highly organized internal 



organs. The mouth 

 is surrounded by a 

 circle of tentacles 

 that have the func- 

 tion of creating cur- 

 rents in the water, 

 on which food and 

 oxygen are carried 

 to the animal. The 

 circle of tentacles 

 is called the lopho- 

 phore (Fig. 115, 1). 

 From the mouth 

 the food passes 

 by a short gullet 

 (Fig. 115, 3) to the 

 stomach. The in- 

 testine is bent on 

 the stomach in 

 such a way that it 

 opens on the ex- 

 terior (Fig. 115, 4), 

 just outside the 

 circle of tentacles, 

 giving the whole 

 FIG. 115. Plumatella. Upper portion of figure alimentary canal 

 much enlarged; lower portion, slightly enlarged, something" of the 

 (After Allman) 



appearance of the 



letter I). Other 

 organs are a gan- 

 glion between the mouth and the anus, a pair of nephridia for 

 excretion, an ovary and a spermary, muscles which withdraw 



1, lophophore ; 2, chitinous sheath; 3, gullet; 4, anus; 

 5, statoblast 



