PRODUCTION 01^ N^W SPECIES. 295 



until such time as I have accumulated a sufficient body of observations to 

 warrant it. 



A careful consideration of the various lines of experimentation recorded 

 and of the pedigree cultures and the data from observation in nature 

 irresistibly forces one to the conclusion that in these beetles the only 

 variations of permanence are germinal, and that the only possibility of 

 evolution is through germinal variations. Those germinal variations which 

 arise in nature are permanent, and the same variations, of the same degree 

 of permanence, are produced in experiment. The diverse kinds of evidence 

 produced in this and in preceding chapters all go to show that under varying 

 conditions of their surroundings these beetles vary, and that as they become 

 more and more extreme an increasing percentage of striking, permanent 

 variations is found; and as I have just shown, it is possible in experiment to 

 produce in this same way a variety of permanent modifications. From all 

 this evidence, however, there nowhere appears the least trace of a suggestion 

 of any specific action of the conditions of existence, but everywhere there 

 appears only the action of environm.ent as a stimulus, while the response is 

 entirely determined by the organism. All of these variations of purely tem- 

 porary and of permanent kinds resolve themselves into responses of the 

 organism to the stimuli of its environment, but the nature of the response 

 is entirely determined within the organism. It is true that different inten- 

 sities of the same stimuli call forth different responses, but, as is shown in 

 the chapter on coloration, the response is entirely determined within the 

 organism, which is adjusted to different intensities of stimuli and reacts 

 according to its own method and on the basis of its own constitution, there 

 being no specific reaction called forth by a given stimulus. 



I conclude, in the light of these experiments, that the production of herita- 

 ble variations, slight or extreme, represents in these beetles the response of 

 the germ plasm to stimuli. In my experiments these stimuli were external, 

 but there is no a priori reason why they might not also be internal. The 

 response, however, is absolutely determined within the organism. 



Since the above statements were written, MacDougal (1906) has given a 

 preliminary account of his experiments with Raimannia, wherein salt solu- 

 tions were injected into the ovule just previous to fertilization, with the 

 result that variations, ''potentially new species, were secured as a result of 

 chemical and osmotic action exerted on unfertilized ovules." These results, 

 he believes, "demonstrate conclusively that factors external to the proto- 

 plast may exert a profound influence upon its heredity characters, and call 

 out qualities not hitherto exhibited by the line of descent affected." These 

 results of McDougal's exactly confirm in plants the results that I have 

 obtained in these beetles, so that the point is now doubly certain that heritable 

 variations are produced as the direct response to external stimuli. In my 



