286 University of California Puhlications in Zoology [Vol. 20 



fibers pass both posteriorly and anteriorly into the ectoplasmic mass 

 of the oral plug. These branches make no observable connections, but 

 seem to fade out in the ectoplasm. Morphological evidence would 

 indicate that this fwrtion of the neuromotor apparatus is concerned 

 solely with the activities of the very mobile oral plug. The adaral 

 ciliary fiber {ad. oil. /., figs. I and J) also arises from the motorium. 

 This fiber attaches to the motorium just anterior to the constriction. 

 It passes directly to the basal granule of the first cilium of the adoral 

 row from which it passes on and makes connection with each of the 

 basal granules of the entire row. It turns inward following the row 

 of adoral cilia along the dorsal or left-hand margin of the membrauelle 

 area. Here its course is exceedingly hard to determine, but like the 

 circumoesophageal fiber, some sections seem to show its connection 

 with the posterior end of the motorium. 



The remainder of the neuromotor sj-stem is not directly connected 

 with the motorium. The adoral ciliary rootlets {ad. cil. r., fig. I) pass 

 inward from the basal granules of the adoral cilia through the ecto- 

 plasm of the apical cone into the endoplasm and well into the posterior 

 third of the organism where they end, not abruptly but by fading out. 

 There is absolutely no indication of any attachment of their inner 

 ends. Just posterior to the middle of the cell there is usually a very 

 distinct crossing of the ciliary rootlets from the opposite sides of the 

 peristome. Each of these adoral ciliary rootlets bears a decided enlarge- 

 ment at the point where it pa.sses from the ectoplasm into the endoplasm. 

 The aggregation of these enlargements gives the appearance in cross- 

 sections through this region (pi. 27, fig. 6) of a zone of large, deeply 

 staining granules about the oesophagus. Each of these enlargements 

 gives rise to a fiber which passes radially outward in a transverse 

 plane. These have been termed the radial fibers {rod. f., fig. J ; pi. 27, 

 fig. 6). Each of these radial fibers as it passes peripherally connects 

 with small enlargements of the rootlets of the cilia of the apical cone. 

 The rootlets of the cilia of the apical cone are like those of the adoral 

 cilia except that they shorten progressively as they near the periphery, 

 at which point they scarcely extend into the endoplasm at all, becom- 

 ing identical with those of body cilia. Since the radial fibers and the 

 enlargements of the ciliarj' rootlets lie in the plane of contact between 

 the ectoplasm and the endoplasm they very clearlj^ mark the limit of 

 the two. At the peripherj' the radial fibers turn posteriorly and 

 become lost in the granular band. This last fact is very suggestive, 

 since the terminal enlargements of the rootlets of the body cilia lie in 

 these granular bands. 



