22 . ELEVENTH REPORT. 



This does not imply that the line may not give off side branches or may not 

 bifurcate into two lines. But while we represent such ramifications by 

 branching lines in our genealogical trees, it must not be forgotten that each 

 of these branches, considered only with reference to itself, forms a direct 

 line from ancestor to descendant.'' Again "The direct, unswerving way in 

 which develojjment proceeds, however slowly, is 7iot suggestive of many 

 trials, and failures in all directions save one." And lasth' these facts at 

 least suggest the possibility that individual variations are not incipient 

 species, but that the causes of the transformation lie deeper and act with 

 considerable uniformity upon large numbers of individuals. It may, perhaps, 

 be the outcome of future investigation that, while variations are due to the 

 union of changing hereditary tendencies, mutations are the effect of dyna- 

 mical agencies acting for long in a uniform way and the results controlled l\v 

 natural selection." This last may be taken almost as a definition of Neo- 

 Lamarckism as it now stands. Concerning this idea of mutation which he 

 adapts from Waagen, Scott says "Another very obvious objection to the mode 

 of evolution here suggested lies in its apparent appeal to a mystical directing 

 force which makes for differentiation or simplification, as the case may be, the 

 nature of which we can hardly hope to learn. Such mysterious forces are only 

 to be admitted when there is absolute!}" no escape from them. The notion of 

 a directing factor in evolution may be altogether illusory and yet it is difficult 

 to shake it off. It is continually appearing in one form or another in the 

 writings of those who do not explicitly acknowledge it and are perhaj^s hardly 

 conscious that their views imply it. The later theories of Weismann neces- 

 sitate its assumption in some shape. But this force may after all be only 

 the expression of some general law which has not l^een formulated, but if it 

 is real, we shall not advance our science l)y shutting our eyes to it." 



Osborn has contributed a considerable numl^er of most valuable essays 

 all directed toward the emphasis of an iinknown factor in evolution. He 

 says ''If Lamarckism fails to explain the origin of variation then we must 

 seek for an unknown factor." In another place he says "The main trend of 

 evolution is determined not by the transmission of the full adaptive modifica- 

 tions themselves as Lamarck supposed, but l^y the disposition to adapti^'e 

 atrophy or hypertrophy at certain points." 



In his paper on Homoplasv as a Law of Latent or Potentical Homology 

 Osborn says "cases of inde])endent evolution of apparently homologous 

 organs I recently proposed to signify as potential or latent homology Isor- 

 rowdng the term latent from Galton as indicating a germinal rather than a 

 ])atent or adult character, and the physical term potential as expressing the 

 innate power or capacity to develop certain organs." This idea he later 

 found to be covered almost exactly by Lankasters term homoplasy and 

 so he adopted that term. On page 265 of the same article he writes "As 

 observed in the evolution of the teeth, especially, homoplasy appears to be of 

 very great importance, not on the technical ground of uniformity in nomen- 

 clature, but because it seems to coincide with the ]irinciple of definite or 

 determinate evolution, a jjrinciple which may l^e of wider application. Oii 

 page 267 of the same article we have with regard to the molar teeth "I have 

 pointed out * * the significant fact that new cusps of the molar teeth do 

 not appear at random, l^ut at certain definite points; that they are at first so 

 minute that they can barely be perceived, so that it is difficult to theoreticall}" 

 assign them a survival value in the struggle for existence ; that the Lamarck- 

 ian explanation is the only one which can be offered; I laid the chief stress, 

 however, not upon the mechanical explanation, l:)ut ujwn definite or deter- 



