232 MICROSCOPY FOR BEGINNERS. 



by reflected light as an opaque object. It is exquisitely 

 beautiful in this position, as is Pectinatella or any of 

 the Polyzoa ; but the animals are very timid. To see 

 the expanded tentacles will therefore demand much 

 time and patience. Plumatella is almost as common as 

 Pectinatella. A board or log that has been floating 

 undisturbed in the pond will, during the summer, be 

 quite sure to afford a rich harvest of Plumatella if its 

 under-surface be examined. 



4. FBEDEBICELLA. 



The colonies of this Polyzoon are found in the 

 shadiest places and near the shores of shallow ponds, 

 growing like Plumatella, and often in company with it, 

 on the lower surfaces of floating or submerged objects. 

 The whole colony may be adherent, or only the base, the 

 stem and branches then floating. A single animal in- 

 habits each hollow branch, and resembles Plumatella in 

 appearance and structure. It may be distinguished 

 from Plumatella, however, by the oval or nearly circu- 

 lar lophophore, that of Plumatella being horseshoe- 

 shaped. The colonies are usually small, covering a small 

 space. The tentacles are never more than twenty-four 

 in number. The statoblasts are more or less circular, 

 and are without spines or hooks. 



5. PALUDICELLA (Fig. 157). 



These colonies may always be known from all other 

 tube-making Polyzoa by their jointed appearance, each 



