10 VORTICELLA. 



d) A clear globule periodically increasing in size and then apparently 



collapsing. This is the contractile vacuole, an organ for the 

 excretion of waste matter analogous to renal products in the higher 

 animals. Time the pulsations of this vacuole. 



e) The nucleus, a curved or crescent-shaped denser portion of the 



body, best distinguished by staining. 



f) With a higher power of the microscope a differentiation of the body 



protoplasm into a firmer, more uniformly granular ectosarc and 

 a more fluid endosarc is possible. A sort of cuticula invests 

 the whole organism, giving it permanence of shape. The stalk 

 is a continuation of the cuticula and ectosarc. Its central darker 

 core axial fiber is the only part that is contractile. 



g) Particles of food surrounded by food vacuoles in the endosarc. 



These food vacuoles contain water ingested with the food and 

 perhaps also some ferment to assist in digestion. 



REPRODUCTION. Look for free-swimming stalkless specimens with a 

 circle of cilia near the proximal end. The larger ones of these are the 

 results of fission, the smaller of budding, two similar processes in 

 reproduction. You may be able to find Vorticellae undergoing one 

 or the other of the processes. 



Exercise i. Draw a group oj Vorticellce on a small scale. Make 

 other drawings on a larger scale showing a single specimen in the 

 extended position and also in the contracted position. Draw any 

 specimens in the process of fission or 0} budding. 



HINTS ON COLLECTING. Vorticella will usually appear in great 

 numbers in jars or dishes prepared as for Paramcecium and Amoeba. 

 The organism is non-colonial, a characteristic which will serve to 

 distinguish it from the branching, tree-like forms of related genera. 



