244 AQUATIC MICROSCOPY FOR BEGINNERS. 



fies the timid creatures on the slide. The -observer 

 must, therefore, be careful not to touch the table, and 

 to make his examination in a quiet room. The 

 charming creatures will ask a little attention and some 

 gentle treatment, but what they will show with the 

 help of a one-inch objective will amply repay for all 

 the outlay of time and of patience. 



The following Key to the genera will help the stu- 

 dent to name the forms he may find. 



Key to Genera of Fresh-water Polyzoa. 



1. In a jelly-mass (a). 



2. In adherent, branching cylindrical tubes (b). 



3. In adherent, branching colonies formed of tubular, 



club-shaped cells (1;). 



4. In attached, pendent stems formed of urn-shaped 



cells [d). 

 a. Jelly-mass rounded, adherent, often very large. 



Pectinate'lla, 1. 

 a. Jelly-mass long, narrow, slowly traveling. Cris- 



tate'lla, 2. 



a. Jelly-mass small, sacciform, finally lobed or 



branched. (Very rare). Ldpkop.us, 3. 



b. Lophophore horseshoe-shaped. Plumatella, 4. 



b. Lophophore circular. Fredericella^ 5. 



c. Lophophore circular, tentacles in a single row. 



Paludice'lla, 6. 



d. Lophophore circular or oval, tentacles in a single 



row. Urnat^lla, 7. 



I. PeCTINAT^LLA MAGNfFICA (Fig. i6g). 



The appearance to the naked eye of the colorless 

 jelly-like substance surrounding the bodies, and of the 

 animals themselves, has already been referred to. 



