30. Cells not separated by semi-opaque deposits of mucilage Oocystis ( part ) 



31. Cells lunate or sickle-shaped, with their convex 



surfaces apposed Selenastrum 



31. Cells straight, in fascicles or irregular clusters, sometimes 



twisted about one another Ankistrodesmiis ( part ) 



32. Angles tipped with 4-6 fine, hair-like bristles Polijedriopsis 



32. Angles tipped with 1, 2, or 3 short, stout spines Tetraedron (part) 



ZOOCHLORELLA Brandt 1882, p. 140 

 Unicellular; spherical or ovoid; inhabiting the cells and body cav- 

 ities of animals. Chloroplast (sometimes 2) a parietal plate covering 

 only a portion of the wall; pyrenoid usually present. Reproduction 

 by aplanospores, as in Chlorella. 



This group, with justification, is regarded by some students as 

 being congeneric with Chlorella. It is arbitrarily separated here and 

 the name retained in order to provide a distinct category for the 

 endozoic species. The phenomenon of 'green' animals, such as Hydra, 

 Ophrydiiim, Spongilla, etc., is invariably referred to as being caused 

 by Zoochlorella. Long usage, therefore, seems to warrant the sepa- 

 ration. The relationship between species of this group and various 

 animals is apparently definite and not haphazard. The symbiosis may 

 vary from commensalism to parasitism. Although the species are 

 described as having no pyrenoid, our specimens usually showed 

 this body very clearly, especially in larger cells. 



Key to the Species 



Plants inhabiting Hydra; cells S-6fi. in diameter Z. conductrix 



Plants inhabiting Ophrydium, Spongilla, and Stentor; 



cells 1. 5-3/11 in diameter Z. parasitica 



Zoochlorella conductrix Brandt 1882, p. 140 

 PL 53, Fig. 10 

 Cells globose or broadly ovoid, usually densely compacted with 

 the cells of Hydra; chloroplasts 1-2, usually with a pyrenoid; cells 

 3-6/x in diameter. 



Common; in green Hydra; inhabiting ponds and swamps where 

 there are dense beds of aquatic vegetation. Mich., Wis. 



Zoochlorella parasitica Brandt 1882, p. 140 

 PI. 53, Fig. 9 



Cells ovoid, inhabiting Ophrydium, fresh- water sponges (Spong- 

 illa), and Stentor spp.; chloroplast 1 (rarely 2); cells 1.5-3/a in 

 diameter. 



Common in Ophrydium, a colonial ciHate which forms floating 

 or attached gelatinous masses 1-10 cm. in diameter. Sometimes the 



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