150 



ZOOLOGY. 



FIG. 68. 



FIG. 68. A, Vorticella, a stalked ciliate Infusorian: i, contracted; 2, extended. /, 

 food "vacuoles"; g, gullet; m, contractile fibre (muscular); n, nucleus; o, mouth, sur- 

 rounded by ciliated disc; p.v., pulsating vacuole; s, stalk. B, a colonial type similar 

 to Vorticella. 



Questions on the figures. Compare the internal structure of Vorticella 

 with that of Paramecium (Fig. 66). What are the principal differences? 

 Likenesses? How is a colonial type (as B) formed? How are new colonies 

 started? In what way does the animal become extended after contraction? 

 Compare living animal. 



FIG. 69. A, Euglena viridis, a flagellate Infusorian. i, typical swimming condition; 

 2, somewhat contracted; 3, spherical resting condition; 4, encysted stage in which fission 

 has taken place, c, cyst; /, flagellum; n, nucleus; o, mouth; p.v., pulsating vacuole; 

 sp, pigment spot. 



B, Podophrya, a stalked Infusorian bearing tentacles (f). p, Infusorian captured 

 for food; s, stalk. 



Questions on the figures. How does multiplication in Euglena differ 

 from that of Paramecium? What are the differences in the method of 

 feeding employed in Vorticella and in Podophrya? What is the structure 

 and function of the tentacles in the latter? 



