GERMINAL SELECTION 139 



of certain structm-es, to a complete disturbance of the harmony of 

 the parts, and ultimately to the elimination of the species. 



It must be admitted, however, that Emery was probably right 

 when he directed attention to the possibility of a 'conflict between 

 germinal and personal selection.' It is quite conceivable that in 

 cases of useful variations, that is, of adaptations, the processes of 

 selection within the germ-plasm may lead to excessive developments, 

 which personal selection cannot control, because, on account of their 

 earlier usefulness, they have in the course of a series of generations 

 and species become fixed not only in a majority of ids, but in almost 

 all the ids of the collective germ-plasm of the species. In this case 

 a reversal must be difficult and slow, for the gathering together of 

 ids with relatively weaker determinants can only take place slowly, 

 and it is questionable whether the species would sm-vive long enough 

 for the slow process to take efiect. But, apart from the question 

 of time, such a reduction of an excessive development would some- 

 times be quite impossible, for the simple reason that there is nothing 

 for personal selection to take hold of. 



Doderlein has pointed out that many characters go on increasing 

 through whole series of extinct species, and ultimately grow to such 

 excess that they bring about the destruction of the species, as, for 

 instance, the antlers of the giant stag or the sabre-like teeth of 

 certain carnivores in the diluvial period. I shall have to discuss this 

 in more detail in speaking of the extinction of species ; it is enough 

 to say here that such long-continued augmentations in the same 

 direction can never be referred solely to germinal selection, since it is 

 hardly conceivable that a species — much less a whole series of species — 

 should arise with injurious characters ; they would have become 

 extinct while they were still in process of arising. Although we see 

 that the Irish stag, with his enormous antlers over ten feet across from 

 tip to tip, was heavily burdened, we are hardly justified in concluding 

 that the size and weight of the burden on his head tended to his 

 destruction from the first — for in that case the species would never 

 have developed at all — but it may well be that at some time or other 

 the life-conditions of the species altered in such a manner that the 

 heavy antlers became fatal to it. In this case the variation-direction 

 which had gained the mastery in all ids could no longer be sufliciently 

 held in check by personal selection, because the variations in the 

 contrary direction would be much too slight to attain to selective 

 value. Sudden, or at least rapidly occurring changes in the conditions 

 of life, such as the appearance of a powerful enemy, exclude all chance 

 of adaptation by the slow operation of personal selection. 



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