352 THE PHILOSOPHY OF BIOLOGY 



observed and calculated frequency distributions may 

 be very much alike. 



In biological investigation, far more than in physi- 

 cal investigation, we deal with mean results. It is, 

 however, just as important that the mean should be 

 considered as the individual divergences from the mean. 

 We want to know the mean results, and the way and 

 the extent in which the individual results diverge 

 from the mean. 



There is a mean or " ideal " result, but we must 

 think of a great number of small independent causes 

 which cause the actually obtained results to diverge 

 from this mean. If these small un-co-ordinated causes 

 are just as likely to cause the results to be less than the 

 mean, as greater than the mean, we shall obtain a fre- 

 quency distribution resembling the one given above, 

 in that the variations from the mean are equal on both 

 sides of the mean. But if the general tendency of the 

 small un-co-ordinated causes is to cause the results, on 

 the whole, to tend to be greater than the mean, then the 

 frequency distribution will be " one-sided," that is, if 

 we represent it by a curve the latter will be an asym- 

 metrical one. Curves which are asymmetrical are those 

 most frequently obtained in biological, statistical 

 investigations. 



MATTER 



Our generalised notion of matter is that it is the 

 physical substance underlying phenomena. Immedi- 

 ately, or intuitively, we attain the notion of matter 

 because of our perceptions of touch, and our perception 

 of muscular exertion. The distance sense-receptors, 

 visual, auditory, and olfactory, would not give us this 

 intuition of matter. 



