I20 AQUATIC MICROSCOPY FOR BEGINNERS. 



used only for capturing food. Yet it slowly floats 

 across the field of view, seldom changing its shape: or 

 it remains suspended almost stationary in the water 

 with all its rays extended, and so resembling the 

 pictures of the sun in the almanac that it has received 

 the name of the "sun animalcule." The rays are sel- 

 dom entirely withdrawn. 



It feeds on smaller animals and upon the spores 

 of Algse. When an animalcule comes in contact with 

 the rays it seems to lose some of its power of motion. 

 It appears to become partly paralyzed, then gliding 

 down the ray, often surrounded by a small drop of 

 protoplasm until it nears the body, when a larger wave 

 flows out and receives it. The little masses of digest- 

 ing food can be seen Jnside the body, where the green 

 color usually turns to brown. 



5. AcTiNOSPH^RiUM Eichh6rnii (Fig. q6). 



At first the reader will confound this Rhizopod with 

 Actinophrys sol, which it resembles in appearance 

 when seen with a low-power objective. It is larger 

 than the' "sun animacule," but this is a distinction of 

 no value unless the observer has happened to find 

 Actinophrys first, and to have become familiar with its 

 appearance and structure. In Actinosphcerium, how- 

 ever, the ray-like pseudopodia are remarkably large 

 and coarse, tapering to their free end from a thick- 

 ened base at the surface of the body. 



The body itself, as the student will notice if he. uses 

 a ^-inch or a |-inch objective, is formed of an ex- 

 ternal layer of large vesicles or bubbles, and a central 

 mass of smaller protoplasmic bubbles. In this bubble- 

 like structure it also resembles Actinophrys, but it 



