334 University of California Publications in Zoology [Vol. 20 



INTRODUCTION 



Paramaeciutn, because of its universal occurrence in aquaria and 

 tlie ease with which it may be cultured, has long been a favorite 

 organism for use in class instruction and laboratory investigation. 

 It is well adapted for this study because it is a generalized rather 

 than a highly specialized tj'pe. For the same reason a description of 

 the system of neuromotor fibers in Paramaecium, a system equalling 

 in complexity the nervous sj^stems of many of the lower Metazoa, will 

 be of general interest. 



Acknowledgments 



The present work was conducted during the past two years at the 

 University of California under the direction of Dr. Charles A. 

 Kofoid, and to his profound insight most of the discoveries were dne. 

 Dr. Charles V. Taylor rendered invaluable assistance in explaining 

 and demonstrating micro-injection and micro-dissection equipment. 

 The fixing, staining, imbedding, and sectioning were directed by Dr. 

 Olive Swezj^ whose expert advice in the use of Heidenhain's iron 

 haematoxylin made possible the wonderfully clear differentiation of 

 the neuromotor fibrils. Professor A. B. Domonoske, of the Depart- 

 ment of Mechanical Engineering, Mr. H. N. Cooper, Curator of the 

 Department of Physical Chemistry, and Mr. W. J. Cummings also 

 gave much appreciated assistance on technical matters of apparatus. 



Eeview op the Literature 



A review of most of the literature on conductile fibers in the 

 Protozoa was written by Dr. Taylor (1920). The only addition made 

 here is a discussion of some of the papers pertaining particularly to 

 Parafnaecium. 



In 1902 Neresheimer made attempts to stain nerve elements in 

 Paramaecium, Spirostomiim, and Stentor coeruleus with Mallory's 

 triple stain. He foimd certain myonemes in Stentor and Spirostomiim 

 but failed to find any in Paramaecium. He concluded, therefore, 

 that none were present and set about to prove this by the following 

 method: He treated both Paramaecium and Stentor with equally 



