BEHAVIOUR OF CELLS 5 
Here we have what a zoologist would describe as a 
specialized mode of behaviour of the nuclei; and we have 
also the behaviour of the minute creatures (which contain the 
nuclei) as they approach each other and come together in 
conjugation. Can one wonder that the latter, at any rate, has 
been regarded as an example of conscious procedure? In 
truth we do not know in what manner and by what subtle 
influences the Paramecia are drawn together in conjugation. 
But it is scarcely logical to base on such ignorance any posi- 
tive assertion as to conscious attraction. It is better to 
confess that here is a piece of organic behaviour, the exact 
conditions of which are at present unexplained. 
We may take from the writings* of Dr. H. 8. Jennings; 
of Harvard, some account of other modes of behaviour among 
Paramecia. They largely feed upon clotted masses of bacteria. 
If a number are placed upon a glass slip, together with a small 
bacterial clot, they will be seen to congregate around the clot 
and to feed upon it. All apparently press in so as to reach it, 
or get as near it as possible. And if a number be placed on 
another slide without any clot, they soon collect in groups in 
one or more regions, as in Fig. 2,111. It appears as if they were 
actuated by some social impulse leading them to crowd together 
and shun isolated positions. Nay, more; it seems as if, after 
thus collecting and crowding in to some centre of interest, the 
attractive influence gradually waned ; the group spreads, and 
the Paramecia are less densely packed ; the assembly scatters 
more and more, but still seems to be retained by an invisible 
boundary beyond which the little creatures do not pass. 
Furthermore, if kept in a jar, the Paramecia crowd up 
towards the surface where the bacteria clots are floating ; and 
if, beneath the cover glass of a slip on which they are under 
microscopic examination, a drop of liquid be introduced 
through a very fine tube, they will seem either to be attracted 
to it, as in Fig. 2, 1., or repelled from it, as in Fig. 2, 11, 
according to its nature. From alkaline liquids they are 
*. See “The Psychology of a Protozoon,” in the Amer. Jour. of 
Psychology, vol. x., No. 4, July, 1899, and the fuller papers there quoted. 
