THE AIM AND ACHIEVEMENTS OF SCIENTIFIC METHOD. 65 



fine pigments.* Similarly, Vampyrdla Spiroyyrce, only a 

 minute unicellular mass of protoplasm, insists on feeding upon 

 the alga, Spirogyra, and rejects every substitute. t Still mom 

 remarkable is the " behaviour " of Arcella, a unicellular organism 

 protected by a concavo-convex shell which on the concave side 

 is pierced by a hole through which pseudopodia are pushed 

 out. Arcella insists that these pseudopodia shall be attached to 

 something solid, and to secure this end generates bubbles of gas 

 so as to raise one edge of its shell, or, ' if necessary, to turn 

 itself completely over.j 



The last example challenges comparison with the behaviour 

 of the Slipper-animalcule, Paramecium, which has been studied 

 and interpreted by Dr. H. S. Jennings. The Paramecia "feed 

 largely upon clotted masses of bacteria. If a number are 

 placed upon a glass slip, together with a small bacterial clot, 

 they will be sure to congregate around the clot and to feectupon 

 it. All apparently press in so as to reach it or get as near as 

 possible." Moreover, they appear generally to be " actuated by 

 some social impulse leading them to crowd together and shun 

 isolated positions." They display, again, definite likes and 

 dislikes towards the various liquids that may be intro- 

 duced into the water in which they are swimming ; " from 

 alkaline liquids they are repelled ; to slightly acid drops they 

 are attracted, unless the acidity be too pungent." 



Dr. Jennings' interpretation of these performances is anti- 

 thetical to Bunge's explanation of the behaviour of Arcella. 

 It consists in an attempt to reduce the phenomena to cases of 

 " organic response " which are conceived as of the same type as 

 -the orderly reactions of inorganic matter. The Paramecia 



* Op. cit., p. 3. Similarly Professor Japp claimed that the mould 

 Peiiicillium "selects" the right-handed variety of racemic acid, B.A. 

 Report, 1898, p. 817. 



t P. 3. 



IP. 7. 



I quote partly from the account given by Lloyd Morgan, Animal 

 Behaviour, 1900, Ch. I. 



F 



