66 THE AIM AND ACHIEVEMENTS OF SCIENTIFIC METHOD. 



crowd round the bacterial clot if, and only if, in the course of 

 their random movements they are brought in contact with it. 

 This mere contact produces an automatic " lessening* or 

 cessation of the regular movements in all the cilia except 

 those of the mouth-groove and funnel." In a similar spirit 

 Dr. Jennings deals with "the seemingly social assemblages 

 of Paramecia, where there is no such substance to arrest their 

 progress," showing that this phenomenon is nothing more than 

 a special case of the " attraction " which feebly acid solutions 

 possess for the animalculse. Where one or two Paramecia are 

 gathered together, they form a centre for the production of 

 a feebly acid solution of carbon dioxide, which is, as with all 

 creatures, a product of their organic waste ; " and when other 

 Paramecia come, in the course of their random movements, into 

 such a centre they remain there and help to swell^the number 

 in the cluster." After a time the solution in the centre of the 

 group becomes so strong as to be repellent instead of attractive. 

 " The group spreads, and the Paramecia are less densely 

 packed." Finally, to meet the objection that in this attraction 

 and repulsion " at least there is, it may be urged, an element of 

 choice," Dr. Jennings once more takes pains to attribute the 

 phenomena to a definite " reaction " which the cilia of the 

 Paramecia undergo when they reach the boundary of the acid 

 drop. 



The general conclusion which he reaches is, in fact, that 

 " the reactions of Paramecium are, as we have seen, comparable 

 in all essentials with those of an isolated muscle [of a frog] "* 

 and, therefore, that " we are riot compelled to assume conscious- 

 ness or intelligence in any form to explain its activities."! 



22. 



Before leaving the consideration of these specimens of 

 ^antithetical interpretations of the same kind of data we should 



* Amer. J. of Psych., x, p. 515. t Ibid. 



