THE STBUGOLE FOB MXISTMNGE 385 



485. In other words, struggle for existence does 

 not result in death to all but the strongest : it 

 may result in variation. A plant adapts itself to 

 competition as it does to physical environment. 

 Given struggle for existence, — which is inevitable 

 so long as there is propagation, — and physical 

 changes in the earth, — which we know to have 

 taken place, — and it is impossible to conceive of a 

 perfectly stable and immutable creation. There must 

 be evolution. 



485a. The reader must not infer that struggle for existence it- 

 self is here specified as a cause of variation. The subject of the 

 causes Of variations or differences is the most important one now 

 before naturalists, and it is not the purpose of this book to dis- 

 cuss it. There are some persons who believe that struggle for 

 existence is itself a, cause, but others think that it only preserves 

 the most useful of the variations which are already present or po- 

 tentially present. It is enough for the beginner to know that the 

 struggle for existence results in the perpetuation of differ«ices. 



Suggestions. — The pupil should see the struggle for exibcenoe. 

 He should count the dead, and should see what divergencies of 

 characters arise. He has already been instructed (Obs. iv.) how to 

 see it in a tree -top, — by looking. If he wants to see it in separate 

 plants, let him stake off a, bit of ground, — say two feet square, — 

 in rich garden soil, allowing the area to remain untouched, and see 

 what happens. He should count the number of plants which come 

 up ; observe if they are of uniform strength and vigor ; and deter- 

 mine how many kinds there are. He need not know "botany" to 

 be able to designate the kinds ; that is, he need not know the 

 names. He may call one kind A and another B. As the season 

 progresses, count at intervals, and observe if some plants are 

 stronger and bigger than others. The teacher may find statistics of 

 such a weed-world in Essay XIV., ".Survival of the Unlike." 



