152 ^ ie Philippine Journal of Science 1916 



these tables and his discussion, he makes two chief conclusions (p. 320), 

 "The first of which is that the 1 local endemic species have not been — as I have 

 already shown in other ways in other papers — developed in any kind of 

 advantageous response to local conditions, as must have occurred did natural 

 selection obtain." To this conclusion, we will return later. 



(p. 325) "The second conclusion that we may, I think, justly draw 

 from the remarkable Tables which have been set out is that, on the 

 average, the commonness of a species depends upon the time that has 

 elapsed from the period it was first evolved in, or arrived in, the country." 

 And again (p. 340), "The second conclusion drawn is that on the average 

 the commonness of a species depends upon its age from the time of its 

 arrival in, or evolution in, the country. The commonness of any individual 

 species will, of course, also depend upon its degree of adaptation to local 

 conditions, and upon many things which can only be regarded as chance, 

 such as the sudden appearance of new factors, like diseases, etc., in the 

 problem. In other words, on the average, species are developed quite 

 indifferently to local conditions, though it is possible that they may be 

 developed because of those conditions." 



It is the second of these conclusions which unquestionably 

 follows from the, figures that Doctor Willis has collected and so 

 clearly presented. This general idea, that geographical distribu- 

 tion and the age of species are correlated, was explained and 

 used by Doctor Willis in 1907 [Annals of Royal Botanic Gardens, 

 Peredeniya, 4 (1907) 69-76] ; and in the paper now under dis- 

 cussion, page 338, he says: 



In 1907 was the first time, to my knowledge, that they were put forward 

 in so many words, and a proper understanding of them will make a great 

 difference in the handling of problems of geographical distribution. 



As Doctor Willis notes, "there is nothing surprisingly new 

 about these views." In the preceding year, 4 I had made use 

 of the same views, and had done so without reference to literature, 

 because, as far back as my student days, at least two of my 

 professors explained them to us as commonly accepted principles. 

 In the paper just cited, page 62, I note: 



Even geographical characters are useful. The whole of the character 

 of not a few genera, as Prosaptia, Niphobolus, and Acrostiehum, is intel- 

 ligible when, and only when, the habitat is included and recognized as 

 the dominant character of all. More broadly geographical characters are 

 of value too, for no plant has progeny in places inaccessible to its re- 

 productive structures. The relative antiquity of groups, as definable by 

 their present characters, is important evidence in judging their relation- 

 ships. If a species or genus is confined to one locality or one part of the 

 world, it is probably not very ancient. If it has a very wide and con- 

 tinuous distribution, its age cannot be less than sufficient to permit such 

 a dissemination. Our oriental Prosaptia, Acrosorns, Loxogramme, "Schel- 



4 The comparative ecology of San Ramon Polypodiaceae. Philip. Jowrn. 

 Sci. 2 (1907) Bot. 1-76. 



