354 University of California Publications in Zoology [Vol. 18 



very similar to that of the cirri. The minute structure of membranelles 

 has been fully described by Maier (1903) while Griffin (1910) de- 

 scribed them for Euplotes tvorcesteri and as far as I have been able to 

 determine those on Euplotes patella do not vary to any noticeable 

 extent from the descriptions already given for membranelles in other 

 ciliates. Each membranelle is composed of two parallel rows of fused 

 cilia which, like the component cilia of the cirri, are separated by the 

 action of the killing fluids. However, it is, as Griffin (1910) suggested, 

 very difficult to determine whether or not the cilia in the living animals 

 are bound together by a protoplasmic film. The basal granules of 

 each membranelle are arranged in two parallel rows just beneath the 

 surface of a furrow formed between two granular ridges of ectoplasm. 

 Such ridges are very distinct when seen in section (pi. 14, fig. 2) and 

 their granular structure is very prominent when viewed from the 

 ventral side. Such a granular structure probably has the same signifi- 

 cance as that discussed in connection with the six longitudinal ridges 

 associated with the anal cirri, namely a reserve supply of material 

 which upon oxidation furnishes energy necessary for the continuous 

 rapid movements of the membranelles. The granules of these ridges 

 are not to be confused with the basal granules of the membranelles. 

 The latter granules are definitely arranged in parallel rows and are 

 distinctly smaller than the granules of the ridges which are irregularly 

 arranged and are similar to the ectoplasmic granules distributed over 

 the whole body. When stained with acid fuchsin the basal granules 

 of the membranelles become bright red, as do those in the basal body 

 of the cirri, indicating a similarity in composition and also in function, 

 as will be pointed out later. Joining the inner ends of all of these rows 

 of granules is a granular fiber which continues around the anterior 

 end of the cytostome and joins the outer end of the motorium. A 

 fuller description of this fiber will be given later in connection with 

 the neuromotor apparatus. This system of membranelles, which is 

 unified by the connecting fiber, waves in such a way that a current of 

 water is set up in the cytostome and the heavy food is carried into the 

 pharynx and thence on into the endoplasm. 



Structure of the Neuromotor Apparatus. — We turn now to a con- 

 sideration of the neuromotor apparatus, a structure to which is 

 attributed the function of coordinating the movements of the above 

 described motor organs. The first part of this to be described is a 

 bilobed body lying in the right anterior part of the organism, to which 

 certain fibers which will be described later are joined. This structure 



