344 University of California Publications. [Zoology 



STRUCTURE. 



It is the intention in the following acconnt of the structure 

 to touch only on those points that will be used later in the disc\is- 

 sion of movements. For more details relative to the ciliary and 

 ectoplasmic structures, reference is made to Maier ( :03) and 

 Schuberg (:05). Throughout this part of the work I have fol- 

 lowed the methods of INIaier and have also used his terminology. 

 He did not include Condylostoma in his investigations, but the 

 elements of structure of this species are essentially the same in 

 many respects as in Stentor, Spirostomnm, and Stijlonychia. 



General Descriptiot.—The body of the animal is compressed 

 dorso-ventrally, and very much elongated, the length usually 

 exceeding the width seven times. The animals vary in length 

 from 400 to 900/t, the average size being from 500 to GOO/j.. These 

 dimensions are somewhat larger than those given by Stein (73), 

 (376-564/a), or Maupas ('83), (305-495^^^). 



The shape of the body is quite variable, depending on the 

 number of food vacuoles present. The widest part is near the 

 middle, the body tapering quite markedly toward the posterior 

 tip, where it ends in a blunt point. The posterior end is not flat- 

 tened as much as the rest of the body, but is set off somewhat by 

 a sharp bend to the left and sliglrtly ventrad. Near the anterior 

 end there is a slight constriction on the left side. Forward of 

 this point the width of the anterior end is variable, due to the 

 flexibility of the left oral lip of the buccal groove. The whole 

 body is somewhat bent, due to the curvature of the posterior part 

 and the spreading of the left lip of the adoral zone, thus bringing 

 the concave side to the left. The surfaces are easily recognizable 

 as dorsal and ventral, the latter containing a large buccal groove. 

 The shape of the animal has been described in a variety of ways. 

 Stein ('73) has figured it with a long slender body of about the 

 same width in all its parts. The buccal groove on the ventral 

 surface is small, coming to a blunt point at the posterior end. 

 Maupas ( '83) in figuring the same species shows the tapering of 

 the body, but makes it somewhat spindle shaped, thereby em- 

 phasizing too much the narrowness of the anterior end. His; 

 figure shows more nearly the real proportions of the buccal 



