410 THE CONTRACTILE VACUOLE 



organism. Around this are one or two rows of smaller secondary vacuoles, 

 which fuse and give rise to a new primary vacuole following systole. 

 Whether or not these secondary vacuoles originate from granules was 

 not ascertained by von Gelei. Essentially the same relationship between 

 primary and secondary vacuoles in Blepharisma was described by Moore 

 (1934), who made the further statement that excretory granules could 

 not be observed. Both Wenrich (1926) and King (1928) found the 

 vacuoles of P. trichium to be vesicle-fed, although neither author men- 

 tioned the origin of these vesicles. Day (1930) found that the vacuolar 

 fluid reaches the elongated canal of Spirostomiim by the fusion of small 

 vacuoles with the canal throughout its entire length. A similar source 

 of fluid in canals of P. caudatum was also reported, but in neither in- 

 stance was the origin of the accessory vacuoles mentioned. 



Faure-Fremiet (1925) observed the filling of contractile vacuoles in 

 several species of Vorticella by the discharge of small vesicles into the 

 vacuole. These vesicles originate in the wall of the vacuole, and cor- 

 respond to the "mural vacuoles" described by Haye (1930) for Cam- 

 panella. Chilodon, Dogielella, and some of the Ophryoscolecidae. Nas- 

 sonov (1925) also investigated Chilodon and Dogielella, and found 

 structure and mechanism of filling to be somewhat difl^erent from that 

 described by Haye. According to Nassonov, vacuoles in these forms do 

 not appear to have the thick walls described by Haye, nor even to have 

 any sort of membrane, but lie directly in the cytoplasm. However, there 

 is a strongly osmiophilic structure closely associated with them, which, 

 for Chilodon at least, and possibly also for Dogielella, may be mistaken 

 for a thick wall or membrane under certain conditions. In both forms the 

 osmiophilic structure remains essentially unaltered in appearance after 

 collapse of the vacuole. Nassonov observed the origin of accessory 

 vacuoles (the mural vacuoles of Haye) in these osmiophilic structures, 

 and believes them to contribute to the filling of the contractile vacuole. 



Many authors hold that in certain Protozoa, typified by Paramecium 

 caudatum, the question of origin of the contractile vacuole does not arise, 

 since in these forms the vacuole system is a permanent structure. This 

 view is not universally accepted, as will be pointed out later. But, whether 

 permanent or temporary, there still exists a no less fundamental question 

 as to the origin of the fluid which finds its way into these organelles. If 

 the origin of this fluid is associated with granules in many diverse organ- 



