156 THE VICTORIAN NATURALIST, 



the midst of a dead universe, set upon on every side by blind 

 forces. And even in death it is triumphant, for, before it has 

 returned to that dead universe, it has handed on the privilege of 

 living to a portion of itself, and so the struggle goes on throughout 

 the ages. I have said life is no passive condition. Its surround- 

 ings call forth ceaseless activity, otherwise it would die. The 

 struggle for existence is a genuine fact : it is one at least of the 

 great factors which have determined the course of evolution. 

 The long struggle from the dawn of life up to man has ever 

 been upward and onward. Change and decay may be the 

 universal law of protoplasm, and protoplasm forms the physical 

 basis of life, including man and all his activities — physical, in- 

 tellectual, and moral — but written over change and decay there 

 is one other word which illumines the whole page, and that one 

 word is Onward. 



THE STRUGGLE FOR EXISTENCE. 



A bacillus has almost incredible prolificness, if the sur- 

 rounding circumstances such as food, moisture, and warmth are 

 favourable. Take a few drops of a fluid containing a couple 

 of hundred organisms : in 24 hours the number has risen to 

 5,000 ; in 48 to 20,000, and on the fourth day there are millions 

 of them. It has been found that a bacillus will divide in one 

 hour, in the next hour these two have become four, in three hours 

 eight, and so on. In three days, supposing this rate were main- 

 tained — that is, supposing their environment were completely 

 favourable — they would have increased to 4,772 billions, and this 

 mass would weigh 7,500 tons. A few days' multiplication at this rate 

 would equal the earth ; but they don't — some survive and others 

 die. Now, in fluids, w^hen the organisms can move about freely, 

 and successively reach fresh parts of the fluid, they will continue to 

 multiply till they are brought to a standstill by circumstances to 

 which I will refer in a moment ; but on the solid, after growing 

 rapidly for a day or two, the colonies soon cease to increase in 

 size. And the reason for this is not far to seek. Those on the 

 surface are in contact with the air, and shut off from the food,, 

 those below are shut off from the air, and in contact with the food. 

 We know that some grow best in contact with the air, others 

 away from it. Those on the edges are probably prevented 

 from multiplying by the accumulation of chemical products in 

 those behind them. If you plant some yeast in a fluid 

 containing sugar and other substances, so that it is under as 

 favourable circumstances as possible for its growth, that it will 

 continue to multiply and grow, causing fermentation and pro- 

 ducing alcohol, until the alcohol (its own product) reaches about 

 17 per cent. At this point its growth ceases, although the 

 temperature may be right, and there is plenty of sugar left in the 



