294 Undversity of Calif ornia Publicatwns in Zoology [Vol. 20 



progresses posteriorly, they become smaller in size, the secondary 

 enlargement approaches the basal granule as the ectoplasmic layer 

 becomes thinner, and the extension of the rootlet into the endoplasm 

 becomes shorter. The body cilia are smallest and their rootlets 

 terminate in the secondarj^ enlargement. The cilia of the anterior 

 end are highly concerted in action. They beat in such a way as to 

 give the animal a remarkable boring motion which probably serves 

 in the penetration of the mucosa of the intestine. 



7. Both species possess a neuromotor system. This is a highly 

 developed and integrated system consisting of five correlated parts. 

 The motorium, lying within the ectoplasm near the cj'tostome, gives 

 rise to a circumoesophageal fiber. In addition, there is a heavier fib«r 

 which connects it with the basal granules of the adoral cilia. The root- 

 lets of the adoral cilia extend far into the endoplasm, usually well into 

 the posterior one-third of the cell. Where they pass from ectoplasm 

 into endoplasm each adoral ciliaiy rootlet bears an enlargement and 

 from this arises a radial fiber which passes to the periphery, turns 

 posteriorly, and disappears in the granular band of ectoplasm. In 

 passing to the periphery these radial fibers connect with enlargements 

 of the rootlets of the cilia of the apical cone. 



Transmitted Fehrmrij S6, 19S1. 



Zoological Laboratory, University of California, 

 Berlceley, California. 



