90 The Ottawa Naturalist. [August 



or selection from year to year of the most desirable individuals 

 results in a gradual improvement in the race until certain liinits 

 have been reached. 



While natural selection is, without doubt, a. potent factor in 

 the developing or creating of new species in nature, and while its 

 action there may suggest the value of artificial selettion as a 

 means of improving domestic types, yet, it fails to account fully 

 for the existence of our present species. This assertion is based 

 on the following facts: (1) Natural selection is based upon 

 variations which it cannot explain. (2) Certain of these varia- 

 tions cannot have been of any possible use to the individual and, 

 hence, cannot have operated in its evolution. (3) Life, according 

 to certain authorities has not been possible on the earth for a 

 sufficient length of time to allow the development of all of our 

 present species, had these been developed as slowly as w^ould 

 be required by the action of natural selection. (4) The numerous 

 transitional links between species, which would of necessity 

 exist had evolution come about as gradually as would be required 

 by the natural selection of the "fittest," are not found. 



We must, therefore, look to some internal factor upon which 

 to base the laws governing the origin of species. Darwin himself 

 recognized the insufficiencv of his theory at a later date, and 

 attempted to supplement it with his theory of "Pangenesis," 

 but failed to contribute much toward the elucidation of the 

 problem. 



ATTEMPTS TO FIND INTERNAL CAUSES OF VARIATION. 



Passing on from the time of Darwin we find the leading 

 investigators searching for an internal force to explain the origin 

 of variation. The German botanist Nageli was the first to at- 

 tempt to find within the organism itself a force which might 

 account for the appearance of strange characters in the ofl^spring. 

 He assumed the existence within the organism of a tendencv 

 toward progression or perfect development and believed that in 

 accordance with this tendencv organisms are continually varying 

 so as to rise in the scale of nature. He failed, however, in explain- 

 ing the origin of this internal force, so contributed little toward 

 our better understanding of the question involved. 



Another theory is advanced by Mivart to the effect that 

 species have arisen suddenly and not by slow modifications hence 

 the theory of ' ' extraordinary births. ' ' An instance of the applica- 

 tion of this theory is found in connection with an experiment 

 conducted by Dr. Godron, of Nancy, with Datura Tatula, (Purple 

 Thorn Apple) , the seed capsules of which plant are normally 

 covered with spines. Seeds of this plant were sown and produced 

 plants among which was found a plant whose seed capsules were 



