838 Causes and Course of Organic Evolution 



life histories traced and their injurious action successfully 

 combatted; while the fermentation, the nitrifying, and other 

 beneficial organisms have been guided and multiplied in their 

 action. 



Again the higher or multicellular parasitic fungi that cause 

 vegetable diseases are being successfully combatted, and by 

 further skillful treatment may be exterminated. So, if at one 

 time, in the past of human history, the vine diseases, the po- 

 tato, the tomato, the melon, the gooseberry, the cabbage, 

 the pear, and other "blights" promised wholesale extermination 

 for many of his most treasured plants, the future holds out 

 brightest promise, if steady effort be exerted. This effort 

 is also for man one of his best educational agents. 



But in similar manner the varied and abundant animal 

 organisms belonging to the groups of hsemoflagellates or blood 

 parasites of man and lower animals, also the Sporozoa or body 

 parasites, have had their life-histories unraveled to a remark- 

 able degree. 



In like fashion the parasitic worms of man and the domesti- 

 cated animals have become understood and successfully antag- 

 onized.^ From the above standpoints, the past half century 

 has truly been a mutational one of phenomenal portent for 

 the future. 



The enormous waste that has resulted in the past through 

 the ravages of caterpillars and predatory insects in general, 

 also through the attack of rats, mice, and other wasteful mam- 

 mals, will gradually but surely be minimized, till a point is 

 reached when they need no longer be dreaded. This result 

 can and will only be secured through international effort, 

 but the accruing benefit obtained will represent food sufiicient 

 for a population equal to that of China. 



Again, if attention be concentrated on the question of drain- 

 age, irrigation, and water suj^ply, results of the past half cen- 

 tury have been such that the near future will open up sure 

 and projected vistas of noblest expanse. The drainage of 

 extensive river-side and shore areas has yielded millions of 

 rich acres to man's hand. The bad lands of the West, also 



