No. 553] DISTRIBUTION OF THE CTL2ET0GNATB.A 



47 



existence of this need relative to pelagic organisms and 

 their conditions of vertical distribution is readily recog- 

 nized and our first impression may be that the extent of 

 this particular need is exceptional, but an acquaintance 

 with the literature on evolution shows plainly that the 

 need is very general. Indeed, this literature is fairly 

 bulging with evidences of mimicry, protective coloration, 

 natural selection, etc., based upon an abundance of data 

 concerning many organisms as well as their environ- 

 ments, which data, while supporting the hypotheses, 

 rarely include any facts relative to the essentially quan- 

 titative nature of either the organisms or the environ- 

 ments investigated. The mere fact that this sort of data 

 supports a hypothesis and that the logic is sound is not 

 adequate scientific proof that the hypothesis is true, for, 

 as Pearl ('11) and others have demonstrated, logic may 

 carry conviction, be supported by numerous data, and 

 still prove erroneous when the quantitative relations of 

 the facts included in such data are considered. Therein 

 lies the mischief of much of our a priori reasoning rela- 

 tive to evolution, namely, that it causes us to depend so 

 largely upon logic that we overlook or neglect as insig- 

 nificant the quantitative nature of organisms and par- 

 ticularly of environments. Our most urgent present 

 need, therefore, is not so much the accumulation of addi- 

 tional qualitative data as it is an exhaustive and quanti- 

 tative treatment of those facts now at hand. 



While the biometrician and, to some extent, other stu- 

 dents of evolution are treating their data quantitatively, 

 the ease with which large numbers of individuals of 

 pelagic species may be obtained without apparently di- 

 minishing the supply, gives an unusual opportunity to 

 the marine biologist for applying quantitative methods 

 on an extensive scale to many of the important problems 

 of evolution. If all the planktological expeditions would 

 join hands by publishing all the data relative to every 

 haul (those that did not as well as those that did contain 

 the species or group under consideration) and by record- 

 ing the approximate, if not the exact, number of speci- 



