DARWINISM DEFENDED. 179 



and nerves also lengthen. Numerous observations by 

 breeders show that in each organism there resides a capacity 

 of self-regulation, up to a certain degree, which produces a 

 harmonious growth and variation of inter-dependent parts. 

 If a plant is removed to richly fertilised soil it will grow to 

 great size, in the course of which growth all parts are pro- 

 portionally changed so that the general habitus of the plant 

 remains the same. If one allows insect larvae to live on very 

 short food rations, the adult insects will be unusually small 

 but with all the organs of their usual relation to each other 

 as to proportional size. Thus it seems that the single organs 

 are definitely correlated with one another so that in their 

 growth they maintain their relative characteristics. "I 

 have," says Plate, "called this form of organic Zweckm'dssig- 

 keit the unity of organisation." If this quality or capacity 

 is lacking in an individual then it develops into a cripple, a 

 monster, and is killed out by selection. Therefore, if the 

 neck of the giraffe varies so as to be longer, one may fairly 

 assume that, in the case of many individuals, at least, all 

 parts of the neck will share in this variation, although there 

 will naturally be slight individual varyings inside of this 

 general variation. And if the antlers of the stag vary 

 towards a larger size there will simultaneously appear the 

 necessary increase in calcareous materials for all parts of 

 the skull, so that the whole skull will be correspondingly 

 heavier and stronger. 



'The process of evolution may be assumed to be, as it was 

 by Darwin, very slow, so that plenty of time is allowed to 

 selection to produce the necessary coadaptations which may 

 be wanting in the earlier stages of the development. In 

 the case of the enlarging of the stag's antlers there may have 

 been wanting at first the necessary congenital strengthen- 

 ing of the neck muscles but this would come to exist through 

 use. The effects of use would increase, however, only to a 



/ 



certain point, and there would finally come a time when the 



