THE WORLD OF LIFE 457 



had formed the subject of previous lectures ; while they are very easily 

 explained on the general principles now set forth. The explanation is 

 the more easy and complete, because of all the characters of living- 

 organisms, color is that which varies most, is most distinctive of the 

 different species, and is almost universally utilized for concealment, for 

 warning or for recognition. And further, its useful results are clear 

 and unmistakable, and have never been attempted to be accounted for 

 in detail by any other theory than that of the continuous selection of 

 beneficial variations. 



The Dispersal of Seeds 



The subject of the dispersal of seeds through the agency of the 

 wind, or of carriage by birds or mammals in a variety of ways, and 

 often by most curious and varied arrangements, of hooks, spines or 

 sticky exudations almost infinitely varied in the different species, was 

 also briefly treated, since they are all readily explicable by the laws 

 of variation and selection, while no other rational explanation of their 

 formation has ever been given. 



Conclusion 



In concluding, the lecturer called attention to a series of cases which 

 had shown us the actual working of natural selection at the present 

 time. He also explained that these cases were at present few in num- 

 ber, first, because they had not been searched for ; but perhaps mainly, 

 because they only occur on a large scale at rather long intervals, when 

 some great and rather rapid modification of the environment is taking 

 place. 



In the following paragraph he endeavored to summarize the entire 

 problem and its solution: 



It is only by continually keeping in our minds all the facts of nature which 

 I have endeavored, however imperfectly to set before you, that we can possibly 

 realize and comprehend the great problems presented by the " World of Life " 

 — its persistence in ever-changing but unchecked development throughout the 

 geological ages, the exact adaptations of every species to its actual environment 

 both inorganic and organic, and the exquisite forms of beauty and harmony in 

 flower and fruit, in mammal and bird, in mollusc and in the infinitude of the 

 insect -tribes ; all of which have been brought into existence through the unknown 

 but supremely marvelous powers of life, in strict relation to that great law of 

 usefulness, which constitutes the fundamental principle of Darwinism. 



