m THE STRUGGLE OF LIFE 45 



high degree, are thus able to survive desiccation. The 

 endeavour to find the most effective way of " lying low ' 

 is part of the struggle for existence from the animal's 

 side ; the surge of the inanimate forces against a novel 

 obstacle presented is the other side of it. The kernel-idea 

 of the struggle for existence is the clash of life against 

 limitations and difficulties. An elaborated and effective 

 answer-back which all the members of the species are 

 equally able to give has passed from the category of 

 " struggle for existence " in the technical biological sense 

 to the category of " adaptations," but individual im- 

 provements in the answer-back and the clash that ensues 

 must be recognised as constituting the genuine struggle 

 for existence in the Darwinian sense. This reiteration 

 of our point may seem wearisome, but it is interesting to 

 remember that Darwin himself confessed to finding the 

 concept of "the struggle for existence ' peculiarly diffi- 

 cult to keep in mind. 



A shop which had once been used in the preparation 

 of bone-dust was after prolonged emptiness reinstated in 

 a new capacity. But it was soon fearfully infested with 

 mites (Glyciphagns), which had been harboured in crevices 

 in a strange state of dry dormancy. Every mite had in 

 a sense died, but remnant cells in the body of each had 

 clubbed together in a life-preserving union so effective 

 that a return of prosperity was followed by a reconstitu- 

 tion of mites and by a plague of them. Of common little 

 animals known as Rotifers, it is often said, and some- 

 times rightly, that they can survive prolonged desicca- 

 tion. In a small pool on the top of a granite block, there 

 flourished a family of these Rotifers. Now this little 

 pool was periodically swept dry by the wind, and in the 

 hollow there remained only a scum of dust. But when 

 the rain returned and filled the pool, there were the 

 Rotifers as lively as ever. What inference was more 

 natural than that the Rotifers survived the desiccation, 

 and lay dormant till moisture returned ? But Professor 

 Zacharias thought he would like to observe the actual 

 revivification, and taking some of the dusty scum home, 

 placed it under his microscope on a moist slide, and 



