GEOLOGY IN SERVICE OF MAN WATTS 291 



inferior, and probably they must have taken long periods to make 

 wood their advantage. But in all such cases the new forms went for 

 a long period into " retreat," and, in face of the apparent slowness 

 of their evolution and the bitter competition to which they were 

 subjected, it is remarkable that they overpassed the troubles of 

 racial youth, and eventually took the place to which they were 

 entitled in the scheme of life. It seems justifiable to believe that 

 there must have been at least some well-equipped types which did 

 not survive competition in these early stages, but went under with 

 all their promise of future success. We can easily imagine that 

 the survival of such, had it occurred, may have altered the whole 

 course of evolution and produced a life-story very different from 

 that we know to-day, and of which we ourselves form no small 

 part. 



3. Not less remarkable than the period of " retreat " is that of 

 booming development which at last came to each successful modifica- 

 tion. In this connection we can instance the "pleine evolution " 

 of the graptolites, the euechinoids, ammonoids, and belemnoids, 

 the fishes, reptiles, birds, and mammals, each in its own time. 

 Each slowly but surely built up its supremacy, and then wantoned 

 through long ages as the lord of creation in its own element and 

 in its own day. Both the period of sanctuary and the subsequent 

 boom can be closely paralleled by the case of many human inven- 

 tions and in the occupations and history of mankind. 



4. But while there are outstanding cases in which a line of ad- 

 vance is taken that is capable of successive improvements and leads 

 on to continuous success, there are many other instances in which 

 the line of advance, though temporarily advantageous, has only been 

 carried through a limited number of stages, and eventually failed 

 either by its inherent inadequacy or by imposing so heavy a burden 

 on the economy of the organism that it Avas unable to bear the cost. 



The only instance I need quote, though there are many others, 

 is the use of defensive armor, spines, plates, hooks, horns, etc. 

 These provide an obvious method of resistance to attack, and this 

 defensive attitude has been practised by one group of organisms 

 after another, but ahvays with the same disastrous result, the im- 

 position of a fatal strain on the organism to meet renewed, perfected, 

 and more vigorous attack. The spinose graptolites and trilobites, 

 the armored fishes and reptiles, are cases in point, and in the last 

 of these instances, at least, victory rested with tne acquirement oj 

 swiftness xn movement, accompanied by increasing power of attack 

 such as is given by the development of teeth or claws or both. 

 Again and again in the Tertiary Era one group of mammals after 

 another, before, or more usually after, the attainment of great size. 



