FINE STRUCTURE 4I 



bands over the vacuole, one of which opens widely to void its 

 content. Independently, Maupas (1883) discovered these spots 

 which are evidence of persisting pores. Andrews (1948b) noted 

 that rarely two pores may open at the same time as well as that 

 the arrangement of the spots may vary in different individuals or 

 in the same specimen at different times. The presence of these 

 pores is easily confirmed (Fig. 8b). 



CM 



B 



Fig. 8. Excretion in S. coeruleus. 



A. Specimen showing location of contractile vacuole and 

 normal site of cytopyge (i) but also excreting from a second 



opening (2). 



B. Multiple pores in granular stripes, one of which is excret- 

 ing contents of the underlying contractile vacuole. (After 



Andrews, 1948b.) 



All students agree that the vacuole increases in size by the 

 confluence of smaller vacuoles or at least by the draining of their 

 fluid contents into the contractile vacuole. Although not as evident 

 as in paramecia, a system of collecting channels has been des- 

 cribed. In coeruleus, Maupas found variable canals formed by the 

 alignment of adventitious vacuoles which presumably ran together 

 and pushed their fluid toward the contractile vacuole. Johnson 

 confirmed this picture and maintained that in divisions one of a 

 pedally directed line of vacuoles becomes the contractile vacuole 

 of the posterior daughter cell, even before separation beginning to 

 contract regularly but not in synchrony with the old one and 

 acquiring excretory pores in the pigment stripes above. Johnson 

 also described a definite longitudinal canal in roeseli, recalling that 



