346 University of California Puhlications in Zoology [Vol. 20 



unrelated organisms whose life habits are very different similar con- 

 ductile elements should be evolved. The fundamental difference is 

 that so far as is known in Paramaeciitm the neuromotor system does 

 not function in mitosis and division and is not a part of the mitotic 

 apparatus, as in flagellates. 



The system in Paramaecium resembles in many ways that in 

 Diplodinium (Sharp, 1914) and Euplotes (Yocom, 1920). In all 

 three animals a set of fibers runs from a center to the eytostomal and 

 cytopharyngeal organelles and also to the organelles of locomotion. 



Paramaecium is unique among the animals thus far described in 

 possessing an innervated system of defensive structures, the tricho- 

 cysts. It is to be regarded as a generalized member of the ciliate 

 group. The fibers are more numerous and finer and not organized 

 into tracts. The coordinating center is less highly developed and 

 harder to differentiate. 



EXPERIMENTAL 



Three different experimental methods were utilized in attempting 

 to demonstrate that the fibrillar system of Paramaecium is conduetile. 



Micro-In.jection op Vital Dyes 



Micro-injection of vital dyes Avas used to determine whether the 

 fibers take the same stains as do nerve fibers in the Metazoa. Child's 

 method of determining the axial gradient was employed (Child, 

 1916) to find whether or not this gradient in Paramaecium is related 

 to the physiological organization that should exist in an animal with 

 a complex fibrillar sj'stem whose function is to receive and transmit 

 stimuli. The third method is that of micro-dissection similar to the 

 experiments of Taylor (1920) on Euplotes patella. 



Intra Vitam Staining 



Wilson (1910) summarized a method of staining nerves intra 

 vitam in the Metazoa with Grlibler's methylene blue. The stain was 

 injected into the living tissue very soon after the death of the animal. 

 In about twenty minutes to two hours the nerve fibers were stained. 

 The tissues were then fixed in saturated ammonium picrate or 7 per 

 cent ammonium molybdate and dehydrated quickly in 100 per cent 

 alcohol or glycerine. 



