42 



THE AQUARIUM BULLETIN 



This beautiful infusorian, Vorti- 

 cella nebulifera, whose body is not 

 over .07 mm. in length, with a stalk 

 about four times this length, is a 

 common inhabitant of our tanks, 

 especially during the summer. 



Individuals are often found attach- 

 ed by its threadlike stalk to a minute 

 strand of algae or some other aquatic 

 vegetable growth. Oftentimes they 

 will be found in large colonies of 100 

 to 400 animals, all attached by their 

 slender stalk to a large parent stem, 

 which in turn will be attached to some 

 support. The entire colony will be 

 apparent to the unaided eye as a faint 

 cloudy body with a circumference not 

 larger than a good size pin-head. 



The accompanying drawing shows 

 but a section of such a colony, but will 

 serve to give a general idea of its 

 formation. The main stalk, or parent 

 stem, is generally considerably longer 

 than the individual stalks, and is 

 attached to some support. A short 

 distance from its point of attachment 

 the parent stalk begins to divide into 

 numerous branches, each of which ter- 

 minates into the little bell shape 

 bodies. 



Beautiful 

 Microscopic Forms 



By H. A. Van Cott 



i: ;;;;,;;; 



When motionless, which is of rare 

 occurrence, this infusorian resembles a 

 plant to a marked degree, but its great 

 activity soon dispels this impression. 



The body of the V. nebulifera, 

 when extended, has the form of a 

 Tulip. The upper edge, or oral mar- 

 gin, shows the ciliary filaments dis- 

 tinctly, which supply the means, as in 

 all the Ciliata group of Infusorians, 

 both for progression and for drawing 

 particles of food into the interior of 

 their bodies. The vibrations of the 

 cilia of the individuals cause the 

 colony as a body to rotate around the 

 point to which it is attached. 



When feeding, each animal is fully 

 extended (Fig. 4.) with its stalk 

 stretched straight, — the complete col- 

 ony taking the form of an opened fan, 

 as shown in the main drawing. In 

 an instant any one animal may fold in 

 its cilia, contract its stalk in the form 

 of a spiral spring ( Fig. 5 ) which 

 contraction jerks it back to its point 

 of attachment to the parent stem with 

 such rapidity that the eye cannot fol- 

 low the movement even under mag- 

 ihcation. 



Generally the entire colony con- 



