l6o THE BIOLOGY OF STENTOR 



If the anlage has to cross the striping, it is apparent that the 

 structural components of the clear stripes would have to be 

 sundered and the pigment granules pushed aside to make room 

 for the primordium. Much simpler would be merely to have the 

 stripes spread apart and permit the anlage to form parallel to them ; 

 and this does occur in Folliculina ampulla, in which the primordium 

 follows the contour of the stripes (Faure-Fremiet, 1932). In this 

 and other forms (see Lwoif) one could speak of a '' stomatogenic 

 kinety ", if all kinetosomes of the primordium arise in connection 

 with a single kinety. But even in the related Semifolliculina, 

 Andrews (1923) described the oral primordium as cutting across 

 the lateral striping. Also like Stentor, there is in the Ophryoglenids 

 no single kinety which produces the primordium, according to 

 Mugard (1947). In the latter there seems to be good reason for this 

 type of development. Where the primordium site cuts across the 

 lateral stripes these are bent and a small section cut out of each 

 kinety, the sections then combining to form the anlage. This does 

 not occur in Stentor, and there are certainly more membranelles 

 produced than kinetics which are cut by the anlage. Although the 

 anlage of Stentor may come to lie largely parallel to the lateral 

 striping, even those of the '' French school " did not maintain 

 that it arises from a single ** stomatogenic kinety" (Chatton and 

 Seguela, 1940). All we can say at present regarding the elaboration 

 of the membranellar band is that kinetosomes appear from some- 

 where in the rift provided for them, sprout cilia, and align them- 

 selves in a series of parallel rows to make the membranelles. This 

 corresponds to Schmahl's descriptions of Bursaria in which he 

 observed first single cilia with separated basal bodies later coming 

 together as membranelles. 



Normally, the primordium always appears on the ventral side 

 of the cell at about one-third the distance in contracted animals 

 between the mouthparts and the posterior pole. This precise 

 localization of the anlage was emphasized by Schuberg (1890) 

 who correlated it with local differences in the pattern of lateral 

 striping. Thus the primordium appears in what he called the 

 ramifying zone, a zone of abbreviated striping bounded right and 

 left by bands which do run from pole to pole. Schwartz (1935) 

 however has pointed out that as the primordium increases in 

 length its anterior end may overstep the left boundary stripe, so 



