234 FEESH-WATEE EHIZOFODS OF NOETH AMEEICA. 



rarely fork or brancli at the ends, and even more rarely anastomose. In 

 some forms, on the coarser rays, a slow circulation of granules may be 

 detected, proceeding outwardly and inwardly. The pseudopodal rays are 

 commonly very numerous, but are variable in number in the same as well 

 as in different Heliozoans. They usually appear perfectly straight and 

 rigid, but are highly flexible and contractile. The contact of a roving 

 animalcule of some strength will cause them to bend like the hairs of a 

 brush under similar pressure. 



In one form of the Heliozoans, the Actinosphserium, the pseudopodal 

 rays are sustained by a more consistent axial thread, springing from among 

 the superficial layer of vacuolar corpuscles of the body. 



The pseudopodal rays are the organs of locomotion and prehension of 

 the Heliozoans. By their means the animals swim in a slow even manner 

 through the water. Food particles, plant or animal, coming into contact 

 with the rays, adhere, and are drawn by their contraction to the body. 

 When the latter is reached, usually a quantity of clear protoplasm is pro- 

 jected or exudes and envelopes the food, which is then gradually drawn 

 into the body of the animal through the contraction of the exuded proto- 

 plasm. 



Heliozoans commonly multiply by division, as may be frequently seen 

 with the common Sun-animalcule, Actinophrys sol. 



The Heliozoans bear a close resemblance to the marine Radiolarians, 

 and have hence been called Fresh- water Radiolarians; they are, however, of 

 much simpler constitution, and are justly considered by most authorities as 

 forming a distinct order of Rhizopods. 



ACTINOPHRYS. 



Greek, aklin, a ray ; ophrus, the eyebrow. 



Body soft, spherical, composed of a hyaline, colorless, pale, and finely 

 granular protoplasm, with mingled coarser granules and minute oil-like 

 . molecules, and more or less crowded with large clear vesicles or vacuoles. 

 Nucleus central, ordinarily obscured from view by the vesicular structure 

 of the sarcode. A large contractile vesicle at the periphery. Pseudopods 

 numerous, projecting as exceedingly delicate tapering rays, or filamentous, 

 finely granular extensions of the protoplasm of the surface of the body, 

 not branching. 



