]922] Bees: The Neuromotor Apparatus of Paramaecium 347 



To demonstrate the presence of nerve fibers in Paramaecium by 

 modifications of this method, a one-tenth of one per cent solution of 

 the stain was injected into the living animals. They were then 

 examined under oil immersion almost continuously for periods vary- 

 ing up to four hours. As long as the.y lived, the ectoplasmic struc- 

 tures did not stain. The endoplasmic inclusions stained light green. 

 At death, the animals became opaque, so that fibers could not be seen. 



Paramaecium was also placed over-night in a one-four-hundredth 

 per cent solution of the stain. As nearly as could be determined the 

 results were not different from those where micro-injection was 

 practiced. 



Axial Gradients 



Alcohol and other narcotics, e.g., morphine hydroehlorate 1 per 

 cent, antipyrin 1 per cent, nicotine Yxq per cent, and strychnine 1 per 

 cent were used rather than potassium cj'anide in determining the 

 axial gradient (Child, 1916) for two reasons: (1) The animals are 

 slowed down in the narcotics so that they may be more carefully 

 observed. This is not the case with potassium cyanide. (2) Neres- 

 heimer (1902) used the above narcotics, and I desired to check on his 

 experiments, from which he concluded that Paramaecium does not 

 behave in these solutions as do animals with nervous systems. 



According to the conception of gradients, the physiologically 

 anterior end of an animal does not necessarily coincide with the 

 morphologically anterior end, but the former is the region having the 

 highest metabolic rate. Tashiro demonstrated that a nerve fiber has 

 a higher metabolic rate than other structures of protoplasm. He also 

 proved that the gradient in an efferent nerve is from the "center" 

 toward the end organ. In an afferent nerve, this gradient is reversed 

 (Tashiro, 1917). 



From the foregoing, it is clear that if the fibrillar system in 

 Paramaecium is conductile, the physiologically anterior end should 

 be the region of the neuromotor center just anterior to the cytostome. 

 But we should also expect the end morphologically anterior to possess 

 a high metabolic rate because of the presence in this sensitive region 

 of so many fibers which conduct afferent impulses. The avoiding 

 reaction in particular (Jennings, 1906) results from the transmission 

 of contact stimuli from this anterior region and the resulting coordi- 

 nated movements of the neuromotor organs, causing the animal to 

 reverse its direction and then to swim forward in a different course. 



