BEHAVIOUR OF CELLS 3 
IJ.—BEHAVIOUR OF CELLS 
From what has already been said it may be inferred that 
our use of the term “ behaviour” neither implies nor excludes 
the presence of consciousness. Few are prepared to contend 
that the iron filings in a magnetic field consciously group them- 
selves in definite and symmetrical patterns, or that sand grains 
on a vibrating plate assemble along certain nodal lines because 
they are conscious of the effects of the bow by which the 
plate is set in sounding vibration. But where organic re- 
sponse falls under our observation, no matter how simple and 
direct that response may be, there is a natural tendency to 
suppose that the behaviour is conscious ; and where the re- 
sponse is less simple and more indirect, this tendency is so 
strengthened as to give rise to a state of mind bordering on, or 
actually reaching, conviction. Nor is this surprising : for, in 
the first place, organic responses, even the simplest, are less 
obviously and directly related to the interplay of surrounding 
circumstances; and, in the second place, they are more 
obviously in relation to some purpose in the sense that they 
directly or indirectly contribute to the maintenance of life or 
the furtherance of well-being. Now where behaviour is com- 
plex and subserves an end which we can note and name, there 
arises the supposition that it may well be of the same nature 
as our own complex and conscious behaviour. 
Take for example the behaviour of the Slipper-animalcule, 
Paramecium, one of the minute creatures known to zoologists 
as Protozoa. The whole animal is constituted by a single cell, 
somewhat less than one-hundredth of an inch in length, the 
form and behaviour of which may be readily studied under the 
microscope. Thousands may be obtained from water in which 
some hay has been allowed to rot. The surface of the Para- 
-mecium is covered with waving hair-like cilia, by which it is 
propelled through the water, while stiffer hairs may be shot out 
from the surface at any point where there is a local source of 
irritation, as indicated at the top of the accompanying figure. 
