ClIAr. XXVIII. 



CONCLUDING EEMAEKS. 



419 







tie 



r* 



accounted _ for by disuse Laving acted on domestic forms for 

 an msufficient length of time, and partly from their exemption 

 from any severe struggle for existence, entailing rigid economy 

 m the development of each part, to which all sp^ies 2 

 nature are subjected. Nevertheless the law of compensation or 

 balancement apparently affects, to a certain extent, our domes 

 tieated productions. uomes 



We must not exaggerate the importance of the definite action 

 of changed conditions in modifying all the individuals of the 

 same species in the same manner, or of use and disuse. As 

 every part of the organisation is highly variable, and as varia! 

 tons are so easily selected, both consciously and unconsciously 

 it is very difficult to distinguish between the effects of the selec- 

 tion of indefinite variations, and the direct action of the con- 

 ditions of life. For instance, it is possible that the feet of our 

 water-dogs, and of the American dogs which have to travel mucli 

 over the snow may have become partially webbed from the 

 s inn, us of widely extending their toes; but it is far more probable 

 that the webbing, like the membrane between the toes of certain 

 pigeons spontaneously appeared and was afterwards increased 

 by the best swimmers and the best snow-travellers being pre- 



7Zf T° S - "T/ S enCTations - A ^cier who wished to 

 decrease , the size oi his bantams or tumbler-pigeons would never 



Suak ° , T" ng , ' bU * W0Ukl SeIeCt the smalIes t »»*- 

 timef 1 i s P° nta ^ously appeared. Quadrupeds are some- 



" t t f eStltUte ° f Ilair > and h ™ ] ™ feeds have been 



Toui! J ,° reaS ° n t0 believe that this is caused bv 



lose! ^tes^t *£* *? °^ ~ *«P * 



direct S ^zit:^x:^ -i et ? d coid act as a 



that these chan.es mav met \ a "' ; *' h ° WeVCT ' P ° SsMe 

 yearly change of coat 7 , Z ^S^™ * the regular 



this yearly ^ g e or he ST f *?"* .*° *?* ^ «" 



I n,,v nrlrl th • thlck fur of arctic animals, or as 



irZ t^ T jztz\i due to tiie direct act4 ° f a 



tected individuals auZalo preSCTVatl0n of tlle best pro- 



Of nil ii, i g ong accession of generations ? 



t^ mo t tpolTln? ^^ *" ° f ^^ ^ 



structure as well as of ^^ CaSeS ° f ^ de ™ tionS ° f 

 vveu as ot grave monstrosities, we cannot even 



2 e 2 



