438 THE CONTRACTILE VACUOLE 



sentially the same type of structure as that described by Nassonov. The 

 vacuole wall was found to be in the form of a ring deeply blackened 

 by osmium. Following systole, the vacuole collapses, but the wall re- 

 mains quite evident. Small vesicles or droplets appear within the thickness 

 of the wall, fuse together, and thus give rise to the new vacuole. On 

 the other hand, Finley (1934) demonstrated, by means of recognized 

 osmium and silver-impregnation techniques, discrete globular inclusions 

 in the cytoplasm of Vorticella convallaria, V . microstoma, and V . cam- 

 panula. These globules were readily distinguishable from the rod-shaped 

 mitochondria by staining with a mixture of Janus green and neutral red, 

 the globules reacting positively to neutral red and negatively to Janus 

 green, whereas with mitochondria the reverse was true. 



Moore (1931) found distributed through the entire endoplasm of 

 Blepharisma globules with osmiophilic cortices and osmiophobic centers. 

 These structures resist bleaching with turpentine. Only in instances of 

 overimpregnation is the contractile vacuole blackened in this form, al- 

 though paramecia, mixed with the Blepharisma uniformly show black- 

 ened vacuole systems. Where impregnation of the vacuole is produced 

 in Blepharisma, it is readily bleached with turpentine. No evidence was 

 noted by Moore that in these osmiophilic globules lay the origin of the 

 contractile vacuole. In a later investigation, Moore (1934) found that 

 the secondary vacuoles do not empty their contents into the primary 

 vacuole, and thus contribute to its filling; but as contraction of the 

 primary vacuole occurs, the secondary vacuoles move into the place it 

 had occupied, where they coalesce to form a new primary vacuole. No 

 "excretory granules" were observed, but in the earlier work Moore de- 

 scribed osmiophilic globules scattered throughout the cytoplasm. On 

 the basis of these observations, Moore rejects the Nassonov homology for 

 Blepharisma. 



King (1933) found in Euplotes that the vacuoles termed group V, 

 by Taylor (1923) have their origin at the distal ends of a very large 

 number of collecting tubules, located just under the ectoplasm on the 

 dorsal surface of the organism. The presence of these tubules was demon- 

 strated by impregnation with osmium. King believes that these tubules, 

 or canals, like those in Paramecium, are responsible for collection of 

 fluid which ultimately reaches the contractile vacuole. 



In a comprehensive series of observations on the Ophryoscolecidae, 



