7 6 



ELEMENTARY ZOOLOGY 



the thickened, bent-out, upper margin of the bell. This 

 margin is called the peristome. With 

 what is it fringed ? The free end of the 

 bell is nearly filled by a central disk, 

 the epistome, 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 differentia- 

 tion of the protoplasm comprising the 

 body into an inner transparent color- 

 less 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 en- 

 dosarc or of both ? Note the curved 

 nucleus lying in the endosarc. (This 

 may be difficult to distinguish in some 

 specimens.) Note the numerous large 



FIG. *. Vorticelia sp. ; circular granules, the food vacuoles. 

 one individual with Note the contractile vesicle, larger and 



stalk coiled, and one , . A , 



with stalk extended, clearer than the food vacuoles. Note 

 (From life.) ^e thin cuticle lining the whole body 



externally. A high magnification will show fine trans- 

 verse 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 

 peristome and epistome, the flowing or streaming of the 

 fluid endosarc (indicated by the movements of the food 

 vacuoles), the behavior of the contractile vesicle. 



