MICHIGAN ACADEMY OF SCIENCE. • 21 



accounted for on the hypothesis of a greater rapidity of development in the 

 individuals of the species of the extreme type, such stimulus being more and 

 more vigorous in the individuals of the type as we advance toward the same, 

 or ])y a reversed im]iulse of development, where the extreme is characterized 

 by the absence or 'mutilation' of characters." 



The factor emphasized by these writers and their fellow workers is little 

 more than pure Lamarckism. Cope, Ryder, Hyatt, Dall all insisted on the 

 development of structures due to strains induced by the actions of the in- 

 dividuals or due to outside influences, but as shown in the quotations given 

 they had something of the ideas which were later developed. 



In the case of the molar teeth a structure rises bej'ond the influence of 

 environment, devoid of use, and is subject to a wear during ontogeny which 

 reduces its value and yet it reappears in the offspring strengthened and ad- 

 vancing. This process continues apart from and even in despite of the inHuence 

 of environment. This is the crux of the whole thing. A structure rises in 

 a region entirely protected from the action of the environment, and despite 

 a repressive action during the ontogeny of the individual the structure 

 develops to a higher state of usefulness in the phylogeny of the race. This 

 is the fact which Nageli would explain l>y his "internal ])erfecting principle," 

 Eimer by Orthogenesis, Waagen and Scott by Mutation, Osborn by De- 

 finite Variation, Rectigradation and Homoplasy. Each of these is but a 

 minor variant of a common idea. 



Nageli 's idea of an Internal Perfecting Principle we may place behind us 

 as an almost too frank confession of ignorance and a premature confession 

 of inability to arrive at a rational conclusion. 



Eimer's Orthogenesis has been discussed by another this afternoon. The 

 name indicates its relation to the other theories. 



Scott in his paper on Variation and Mutation in 1894 discusses Bateson's 

 great work on the materials for the study of variation and strikingly contrasts 

 Bateson's conclusions drawn from the examples he cites with the conclusions 

 that have been drawn from long phyletic series. He shows that while 

 individual variation may be almost in any direction and may result from 

 the addition as well as the reduction of parts, in phyletic series no case has 

 been observed where there has been other than a decrease in the number of 

 parts. This is particularly evident in the development of teeth and of foot 

 structures. Scott concludes that phyla show an orderly advance in variation 

 toward a definite end. This advance is shown in the morphological mean 

 of the species, or if you please, in the normal individuals. There may be all 

 sorts of minor variations around this but it is the individuals in the line of 

 orderly advance which persist. Scott illustrates this advance as follows: 

 "This mode of viewing the facts may be illustrated by an analogy. The 

 path of a cyclonic storm is determined by the path of the storm center 

 around which the winds circulate, blowing in every direction. These cir- 

 culating winds would represent the vaiiations which occur at every stage in 

 the history of the phylum, while the course of the storm center would repre- 

 sent the phylogenetic change, or nuitation. Thus the cycles of variation 

 tend to repeat themselves, though the center around which they revolve, 

 has a course of its own, dependent, not on the accumulation of those winds 

 which happen to be blowing in the right direction, but upon factors of much 

 greater significance." One or two other quotations will make clear his- 

 idea. "Indeed, the most striking fact about any well established phylum 

 is the directness of its advance towards its final goal, however greatly or in 

 however many directions it .may be varying at any or all stages of its history. 



