40 



COLLEGE ZOOLOGY 



Order 2. Heliozoa. — Rhizopoda with thin, radially ar- 

 ranged pseudopodia, which are usually supported by axial 



threads (Fig. 18, a). Ex- 

 amples: A ctino splicer ium, Ac- 

 tinophrys (Fig. 18). 



Actinophrys (Fig. iS), the 

 sun animalcule, lives among 

 the aquatic plants in fresh- 

 water ponds and ditches. The 

 body appears vesicular, being 

 crowded with vacuoles (c). 

 The small organisms which 

 serve as food strike the 

 pseudopodia, pass down to 



Fig. 18. — Actinophrys sol, a Helio- ,-t •l'j j lr j 



zoon. An individual with a large gastric the bod y> and are engulfed; 



vacuole (g), contractile vacuole (c), and larger organisms (g) are drawn 



axial filaments (a) in the raylike pseudo- . , , .... 



podia. (From Calkins, after Grenacher.) ln b Y se y eral _ neighboring 



pseudopodia acting together. 



Order 3. Radiolaria. — Marine Rhizopoda with raylike 

 pseudopodia, a central perfor- 

 ated capsule of chitin (Fig. 19, 

 sk. 3), and usually a larger en- 

 closing skeleton of silica (sk. 1, 

 sk.2). Examples: Actinomma 

 (Fig. 19), Thalassicolla, Heli- 

 os phtzr a. 



The shells of the radio- 

 larians, upon sinking to the 

 sea bottom, form radiolarian 

 ooze; this becomes hardened, 

 producing rock strata as much 



as IOOO feet thick. These ^o. i 9 .- Actinomma asteracanthion. 



a Radiolarian. The shell is broken 

 rocks may take the form of away so as to show the outer (sk. 1), 



quartzites, flint, or chert COn- middle (^ 2), and inner (jA. 3) spheres 

 " ' ' (From Weysse, after Haeckel and 



Cretions. Hertwig.) 



sh.z 



