PARASITES OF PROTOZOA 



1077 



sion (Brumpt and Lavier, 1936; Stabler and Chen, 1936) is the most 

 important evidence for this benignity. 



No strictly parasitic relationship has been established in any member 

 of the group Heliozoa proper, but Wetzel (1925) discussed as tempo- 

 rary parasitism the association between Raphidwcystis infestans and cili- 

 ates (Fig. 223B). This organism is normally predatory on flagellates 

 and small Infusoria, but when it attacks larger ciliates, such as Para- 

 mecium, Colpidium, Glaucoma, Nassula, and Trachelius, it passes, 



Figure 223. A, trophozoites of Entcunoeba sp. in Zelleriella (after Stabler and Chen, 

 1936); B, Raphidiocystis infestans Wetzel on Paicimecium (After Wetzel, 1925.) 



according to Wetzel, to the parasitic manner of life. The heliozoans 

 become attached by means of pseudopodia to various parts of the body, 

 those pseudopodia gradually shorten, and eventually they lie very flat 

 on the surface. The body of Paramecium may be completely enclosed 

 by many fused Raphidiocystis, which extract dissolved nutriment until 

 only a remnant of the ciliate is left — a process which requires from 

 twenty or thirty minutes to two days — after which the heliozoa disperse. 

 Wetzel discussed the significance of this type of relationship in the 

 phylogenetic origin of parasitism as transitional between strict preda- 

 tism and pure parasitism. 



