HISTORICAL ACCOUNT OF EVOLUTION THEORY 3$ 



three factors: a standstill or cessation of development on the part of 

 some lines; sudden development by leaps (practically mutations); 

 and hindrance or difficulty of reproduction (the type of thing that 

 Romanes emphasized as physiological isolation ten years later). 

 Eimer illustrated his theories by the evolution of color patterns in 

 lizards and those on the wings of butterflies. In both he believed that 

 longitudinal stripes were primitive, that rows of dots followed these 

 which were in turn followed by crossbands, reticular patterns, and 

 finally by solid coloration. This hypothetical phylogenetic order is 

 more or less closely paralleled by the ontogenetic order, in the 

 lizards at least. 



It will be noted that Eimer 's theory places natural selection in a 

 subordinate position, but does not dismiss it altogether, as is done by 

 Nageh. It aids natural selection in explaining adaptations in that it 

 furnishes for natural selection various characters of selective value, 

 which may be either perpetuated or eliminated according to their 



itility. 



E. D. Cope, a leading American palaeontologist of the past cen- 

 tury, had an orthogenetic theory involving his ideas of "bathmism" 

 (growth force), "kinetogenesis" (direct effect of use and disuse and 

 environmental influence), and "archaesthetism" (influence of primi- 

 tive consciousness). It may be said that his ideas were Lamarckian 

 throughout. In common with the majority of palaeontologists of 

 later date — Osborn, Williston, Hyatt, Smith, and others — Cope felt 

 the need of some factor other than natural selection to explain the 

 apparent steady progress of characters in definitely directed lines as 

 seen in the fossils. It is natural therefore that palaeontologists almost 

 universally lay hold of both Lamarckian and orthogenesis ideas. 



Charles Otis Whitman, who, until his death over twenty years ago, 

 was considered the leading American zoologist, had strong leanings 

 toward orthogenesis. In one of his few publications he says: 



"Natural selection, orthogenesis, and mutation appear to present 

 fundamental contradictions; but I believe that each stands for truth, 

 and reconciliation is not far distant. The so-called mutations of 

 Oenothera are indubitable facts; but two leading questions remain to 

 be answered. First, are these mutations now appearing, as is agreed, 

 independently of variation, nevertheless the products of variations that 

 took place at an earlier period in the history of these plants ? Secondly, 

 if species can spring into existence at a single leap, without the assist- 

 ance of cumulative variations, may they not also originate with such 



