THE PEOTOZOA (continued) 



SECTION B. THE HELIOZOA 1 



THE term Heliozoa is commonly used to include a number of 

 Protozoa, generally inhabitants of fresh water, with few characters 

 in common except the possession of straight, radial pseudopodia 

 which rarely anastomose, and the absence of anything like a 

 capsular membrane dividing a central portion of the body from a 



peripheral portion, such as is found 

 among the Eadiolaria. The more 

 highly specialised members of the 

 group have a spheroidal body, which 

 rarely exhibits amoeboid change of 

 shape, divided into a more vacuolated 



FIG. 1. 



Actinosphaerium Eichhorni, Ehrb. A, a drawing 

 of an individual as seen in optical section ; c.^i, a 

 contractile vacuole previous to discharge of its 

 contents ; c. v z , the position of a contractile vacuole 

 that has just collapsed ; e.r, food-vacuole ; r, a 

 rotifer in the act of being engulfed in a food-vacuole. 

 B, a small portion of the ectoplasm of the same 

 animal very much enlarged ; N, the nuclei ; ps, a 

 pseudopodium ; ps.a, the axis of the pseudopodium. 

 The axes of the pseudopodia have been recently 

 traced farther into the ectoplasm than is shown in 

 the figure and into closer relation with the nuclei. 

 (After Leidy.) 



ectoplasm and a less vacuolated endo- 

 plasm, the endoplasm containing one 

 or many nuclei, and sometimes a per- 

 manent centrosoma distinct from the 

 nucleus. The pseudopodia are long, 

 slender, and stiff, projecting radially 

 from the surface of the body, and 

 generally consisting of a cortex con- 

 tinuous with the ectoplasm and an 



axis prolonged into the endoplasm (Fig. 1, ps). In Elaeorhanis, 

 Nudearia (Fig. 8, E, p. 1 0), and some others that may be regarded as 

 being on the border-line between the Heliozoa and Group B of the 



1 By the late Prof. W. F. R. Weldon, F.R.S., and Prof. S. J. Hickson, F.R.S. 



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