348 University of California Publications in Zoology ["Vol. 18 



As indicated above the cytostome is bounded on the left by a series 

 of membranelles {cyt.mem., fig. A). These extend forward from the 

 pharynx to the anterior end of the animal, then around dorsal to the 

 anterior lip to its right hand end. In shape the whole series of mem- 

 branelles reminds one of the lapel and collar of a coat. For about half 

 of the distance along the cytostome these rows of membranelles lie flat 

 with the surface of the animal, but from about the middle of the series 

 posteriorly the whole series twists until the membranelles are at almost 

 right angles to the original position. In the region of the pharynx the 

 membranelles become shorter and in its lower part they become reduced 

 almost to the ciliated surface of the pharynx. In the anterior region 

 the membranelles make another twist. This twist is very much like 

 that which the lapel makes in going around the collar of the coat, and 

 the membranelles are arranged at an angle with the dorsal side of the 

 lip (pi. 14, fig. 7). The minute structure of the membranelles, their 

 method of functioning and their relation to the neuromotor apparatus 

 will be considered in detail in later paragraphs. 



The pellicle {cu., pi. 14, fig. 5) is a rather heavy rigid struc- 

 ture and appears as a distinct line covering the animal completely, 

 thus keeping the shape of the body constant. With Mallory's stain the 

 pellicle colors blue and in sections shows a distinct line exhibiting little 

 differentiation in structure. 



Internal Features 



ECTOPLASM 



The ectoplasm (ect., pi. 14, fig. 5) on the dorsal side of the animal 

 is distinctly set off from the endoplasm. It is about one micron thick 

 and is characterized by the presence of rather large granules, which 

 when viewed in sections form a layer just beneath the pellicle. With 

 Mallory's stain the ectoplasm on the dorsal side takes a bluish tint. 

 Laterally the ectoplasm thins out until ventrally it is scarcely to be 

 distinguished from the pellicle, except in regions immediately around 

 the bases of the cirri. The ectoplasm gives rise to the cirri, mem- 

 branelles, basal granules and fibers in connection with them, as will be 

 shown in a study of the formation of new organelles. Besides these 

 structures the ectoplasm of the dorsal side contains the eleven rows of 

 rosettes of granules mentioned above. Each rosette is composed of 

 from eight to ten granules. In regularly fixed and stained specimens 



