10 PROTOZOANS. 
perfect screw in the operation. They multiply by a sim- 
ple division (Fig. 9, c) or by budding (4, 2). 
Fic. 8.— Paramecium 
bursaria, showing Fic. 9.—Vorticelle. «a, extended; 
cilia. ¢, contractile 6, coiled; c, division; d@,d, free- 
vacuole ; @, food. swimming buds. 
Works on Protozoans for further reference. 
“The Atlantic, and Depths of the Sea,” Sir Wyville Thomson ; 
Carpenter on the Microscope; “Mind in Nature,” H. J. Clark; 
Leidy’s “‘Fresh-Water Rhizopods” ; Pritchard’s “ Infusoria” ; ‘“ Man- 
ual of Invertebrates,” T. H. Huxley ; ‘‘ Challenger Reports”; ‘‘ Even- 
ings at the Microscope,” Gosse ; Thompson’s “ Monthly Microscopical 
Journal” ; ‘‘ The Quarterly Microscopical Journal”; Bastian’s ‘“ Ori- 
gin of Lowest Organisms, and Beginnings of Life”; “ Notices of Pro- 
tozoa,” by Professor Leidy, in “ Proceedings of Philadelphia Academy 
of Natural Sciences” ; ‘“‘ Water turned to Blood by Red Infusoria,” in 
_“ Popular Science Monthly,” vol. iv, p. 202. 
