12 AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



,B XI 



y 



2. GROUP OF VORTICELL.E (from Marshall and Hurst). x 220. 

 L, II., and III. show the animal in various positions ; IV. is a much 

 smaller specimen drawn to the same scale ; V. shows a specimen made 

 to contract by action of alcohol ; VI. is detached from its stalk, and 

 swimming away freely, disc forwards ; VII. , VIII. , and IX. show three 

 stages of fission; X., XL, and XII. show the separated individual 

 swimming by means of the aboral circle of cilia ; XL is slightly con- 

 tracted ; XIL strongly contracted after the cover-glass has been tapped. 

 A, Food-vacuole discharging contents at anus; C, cilia of the disc; 

 C F, contractile fibre of stalk ; D, disc ; D', disc contracted ; F V, food- 

 vacuole ; P H, gullet ; P V, pulsating vacuole ; P, peristome ; M, myo- 

 phan striation ; N, nucleus ; V, vestibule. 



