184 



SCIENCE 



[Vol. LV, No. 1416 



augurs for speed. The water packet is an 

 integral part of the pump. The condensed 

 mercury vapor is returned directly to the boiler 

 through a pin-hole valve shown in the figure. 



Dsrfad Arrmfs Ind':' 

 SofidArro'^ Indieaf^ 



High Speed 



High V/icuum 



r^ercuri/ yapor Pu^p 



Vcrtict,,' f/a-tilc T^-pt 



In the second type, Figure 2, the umbrella 

 is omitted, the delivery tube is short and 

 ends in a central vertical nozzle, and hence the 

 bulb to be exhausted and the fore pump are 

 interchanged. The throat at V through which 

 the hot mercury vapor issues is large but not 

 annular. The water jacket and mercury return 

 are the same as in the umbrella type. 



Some idea of the speed of either pump may 

 be obtained from the following data taken 

 recently: "With a Ceneo-Hyvac oil pump, as a 

 fore pump, a discharge tube of 2.8 liters 

 volume was exhausted from the point at which 

 the mercury vapor pump began to take hold 

 (approximately 1 cm. dark space) to where 

 the tube began to darken (the X-ray stage) in 

 30 seconds. If a mercury vapor trap is inter- 

 posed between the pump and B the time in 

 the above may be reduced to 15 seconds or 

 even less! 



Comparing the two types it was found that 

 the umbrella type seems, in general, to be the 

 more speedy, possibly for two reasons: first, 

 the water jacket reduces the amount of mer- 

 cui'j' vapor that finds its way into the bulb B 

 (this of course may be entirely eliminated by 



the mercury vapor trap mentioned above), and 

 second, the issuing mercury vapor stream is 

 annular. On the other hand the vertical nozzle 

 type is somewhat easier to construct. An ad- 

 vantage of the former, especially for lecture 

 table demonstrations, is that the bulb B to be 

 exhausted is supported centrally over the 

 pump. These pumps are made of Pyrex glass. 



Chas. T. Knipp 

 Laboratory or Physics, 

 TJniveesity of Illinois, 

 December, 1921 



THE NEUROMOTOR APPARATUS OF 

 PARAMECIUM 



This study which commenced with micro- 

 injection experiments on Parameeium has led 

 to the discovery of a complex neuromotor sys- 

 tem in the animal. This discovery is important 

 because Paramecium is a generalized cUiate and 

 yet has attained a degree of structural com- 

 plexity and functional diversity in respect to 

 one organ system comparable at least with 

 that of the lower Metazoa. It is thus again 

 exemplified that the unicellular state is plainly 

 not an essential condition for evolutionary 

 specialization and functional efficiency, except 

 as it places limits on the size of the organism 

 and the developmental processes arising there- 

 from. 



The neuromotor apparatus consists of a 

 neuromotor center situated near the anterior 

 end of the cytostome and at the posterior end 

 of the oral groove; a set of cytopharyngeal 

 fibers which run from the neuromotor center to 

 the membranelles of the cytostome and cyto- 

 pharynx; an oral whorl of peripheral fibers 

 which diverge from the neuromotor center and 

 run to the cilia and trichocysts of the oral side 

 of the body; an aboral whorl of peripheral 

 fibers which diverge from the same center to 

 the cilia and trichocysts of the aboral side. 

 The cilia of the organism arise from grooves 

 in the pellicle which run in nearly parallel 

 lines from the anterior to the posterior end of 

 the lx)dy. Those on the oral side are slightly 

 oblique, meeting in a series of V's in a line, 

 the oral suture, which runs obUquely through 

 the cytostome from the anterior to the pos- 

 terior end of the body. The trichocysts are 

 arranged with reference to the neuromotor 



