1006.] on The Pliyural Bmh of Lifp. 397 



some are innutritions and abselutely useless. But we also notice 

 that there is a decided balance in favour of the nutritious ])article. 

 Like Autolycus, it is a picker-up of unconsidered trifles, ii:nided bv a 

 decided preference for things useful to itself. Therefore, the tiny 

 animal manifests discrimination or choice — imperfect, no doul)t, but 

 clearly recognisable. And the choice is beneficial : it contains an 

 element of purpose. 



Watch an amceba lono^ enoui>-h, and it will be seen to divide into 

 two, and these ao-ain into two, so formiuf^ successive generations the 

 individuals of which resemble one another. These labile, creeping 

 fragments of jelly have recognisable form, and zoologists classify the 

 various forms in so many species, each of which breeds true. They 

 manifest that property of living matter called heredity. 



Lastly, the individual amoeba is in incessant movement, and with 

 each successive generation there is growth of individuals and increase 

 in the mass of living matter. Now, to these three features, choke and 

 purpose, (jrowtli, and herediiy, I propose to confine myself, and I will 

 consider them separately and in the order named. 



The Faculty of Choice. 



In one of Jules Verne's books, which at one time or another held 

 most of us in thrall, there is an account of a submarine vessel which 

 for a long time was conjectured to be some mighty marine monster. 

 Now, I want you to put yourself in a similar position with respect to 

 a model Whitehead torpedo, to consider yourself as meeting one of 

 tliese for the first time and studying its movements under the impres- 

 sion that it is a living being. The torpedo must be without its 

 charge, otherwise your experiments would come to an abnijit end ; for 

 I wish you to consider yourselves as inquiring why this curious beast 

 should always swim at the same depth. Push it down, pull it to the 

 surface, it would presently be swimming again as many inches below 

 the surface as before, and you would say to yourselves. Why on earth 

 does it choose to swim there? 



Instead of a model torpedo, here in a drop of fluid are countless 

 thousands of the most minute forms of life, each actively darting 

 hither and thither, each so small that 5,000 would make only one 

 large amoeba. Into that drop you introduce two fine capillaries, the 

 one filled with very dilute acid, the other with very dilute alkali, and 

 in no very long time you will find that the vibrios have collected in 

 a mass at one or other of the tubes — probably the acid tube. If 

 you followed ordinary nsage, you would express the result again in 

 terms of choice by saying that the animals are attracted to the acid 

 and are repelled from the alkali. 



Both cases illustrate the difficulty in freeing the imagination from 

 the tyranny of the counters it employs. The first case, that of the 



