154 The Philippine Journal of Science me 



indispensable does not in the least impair the fact that fitness is 

 also indispensable. The student uses his time according to his 

 ability, and his fitness for the work of a student becomes effective 

 as time passes. 



Now, likewise, in the case of plants, if the plant be without 

 fitness, time avails it nothing. Assuming the plant to exist, but 

 without fitness to endure and to spread, it stands still for a 

 longer or shorter time and finally disappears. The doctrine of 

 natural selection and survival is a rational one; but would not 

 be so, if it ignored time. The fitness of any plant is merely 

 ability to make use of time in which to survive, to spread, and 

 eventually to keep or to become adapted to the conditions under 

 which succeeding ages find it. There could be no sane doctrine 

 of natural selection without consideration of the element of 

 time; and the early fight of the idea of natural selection for 

 general recognition was forced primarily by the necessity of 

 past time for the possibility of the evolution that natural selection 

 postulated. 



Now, if we recognize, as I do not see how we can possibly 

 escape doing, that the demonstration of a relation between time 

 and geographic distribution not only does not impair the doc- 

 trine of natural selection, but is rather an indispensable and 

 inevitable corollary of the theory of natural selection and a con- 

 sideration that must be taken into account in the application 

 of the theory of natural selection to the understanding of the 

 bionomics of any single plant or structure, I believe there will 

 remain nothing in this paper by Doctor Willis that consititutes 

 an argument against the doctrine of natural selection or that 

 offers anything but an invitation for the investigation of partic- 

 ular problems in the application of this doctrine. 



To some of these applications, I will return presently. First, 

 however, let us note that the difference in view between Doctor 

 Willis and myself lies again in the demand made upon the doc- 

 trine of natural selection or, in other words, upon what we mean 

 by this doctrine. To me, the proposition is simply that those 

 plants survive that can — where, when, and while they can. Their 

 presence is obviously necessary before they can begin to survive. 

 To Doctor Willis, the doctrine of natural selection is something 

 which ought to explain the initial presence of the plants. In 

 passage after passage, he recognizes the necessity of fitness for 

 ultimate survival, sometimes without reservation, sometimes 

 with decided qualification for another element classified as 

 chance; thus (p. 341) : 



