AMCEBA, PARAMCECIUM AND VORTICELLA 43 



tome, with arched upper surface and a circlet of cilia. 

 Between the epistome and peristome is a groove, the mouth 

 or vestibule, which leads into the body. Study the internal 

 structure of the transparent, bell-shaped body. Note the 

 differentiation of the protoplasm comprising the body into 

 an inner transparent colorless endosarc containing various 

 dark-colored granules, vacuoles, oil-drops, etc., and an 

 outer uniformly granular ectosarc not containing vacuoles. 

 Is the stalk formed of ectosarc or endosarc or of both ? Note 

 the curved nucleus lying in the endosarc. (This may be 

 difficult to distinguish in some specimens.) Note the nu- 

 numerous large circular granules, the food particles. Note the 

 contractile vesicle, larger and clearer than the food vacuoles. 

 Note the thin cuticle lining the whole body externally. A 

 high magnification will show fine transverse ridges or rows 

 of dots on the cuticle. 



Make a drawing showing the internal structure. 



Observe a living specimen carefully for some time to 

 determine all of its movements. Note the contraction and 

 extension of the stalk, the movements of the cilia of peri- 

 stome and epistome, the flowing or streaming of the fluid 

 endosarc (indicated by the movements of the food particles), 

 the behavior of the contractile vesicle. 



Make notes and drawings explaining these motions. 



Specimens of Vorticetta may perhaps be found dividing, 

 or two bell-shaped bodies may be found on a single stem, 

 one of the bodies being sometimes smaller than the other. 

 These two bodies have been produced by the longitudinal 

 division or fission of a single body. In this process a cleft 

 first appears at the distal end of the bell-shaped body, and 

 gradually deepens until the original body is divided quite 

 in two. The stalk divides for a very short distance. One 

 of the new bell-shaped bodies develops a circlet of cilia near 

 the stalked end. After a while it breaks away and swims 

 about by means of this basal circlet of cilia. Later it settles 



