36 THE BIOLOGY OF STENTOR 



membranelles take the form of isolated cilia not joined in sheets. 



Dierks granted, however, that the myonemes of the frontal 

 field are continuous into the gullet, proceeding uninterrupted and 

 in a sharply spiraled course to its terminus and also, as in the 

 frontal field itself, showing no branchings (Fig. 6b). In the gullet 

 the myonemes become much thicker and presumably stronger, 

 according to Gelei, and their disposition more or less transverse to 

 the length of the gullet could provide for the peristaltic movements 

 in swallowing which have been observed. Gelei also described a 

 fibrous net surrounding the gullet, which he thought might serve 

 both to prevent the gullet from tearing when stretched and to 

 coordinate cilia and myonemes in a swallowing action. Such an 

 appearance may have been due to the system of vacuoles and inter- 

 spersed fibers found near the gullet by Randall and Jackson. 

 These numerous vacuoles have double or triple membranes and 

 it was therefore suggested that they might be formed by invagin- 

 ations from the gullet wall, as in the pinoc3rtosis of Amoeba. The 

 adjacent fibers run rather deeply into the interior and may 

 represent the pharyngeal fibers of Schuberg. 



Following Schuberg we shall call the inner terminus of the 

 gullet the cytostome. Again in everted gullets, Andrews (1946) 

 saw the cytostome as a thin, clear membrane without visible struc- 

 ture which prevents the escape or regurgitation of endoplasm. 

 Dangling inward from the periphery of this cytostome he found the 

 long fibers described by Schuberg but not seen as such by others, 

 and he thought that they formed part of a permanent canal which 

 guides and might even propel ingested food into the endoplasm. 

 By Andrews' account, ingestion may occur in one of three ways : 

 small particles may collect at the bottom of the gullet and push out 

 the stomal film until it breaks off as a membrane surrounding 

 them; the film may be momentarily broken as objects like small 

 rotifers pass directly into the endoplasm; or the film may be 

 missing as the cytostome opens wide to admit larger organisms 

 or clots of food. In the last two cases the ingested animals thrash 

 around freely in the endoplasm but eventually are encased in a 

 food vacuole and die. I once found a stentor that had ingested a 

 cotton fiber with one end still protruding forward out of the gullet 

 and the other end passing through the cell and emerging through 

 the surface near the posterior end. 



