324 Evolution and Adaptation 



as its powers of resistance are concerned it is a very differ- 

 ent being. 



In regard to the perpetuation of the advantages gained by 

 means of this power of adaptation, it is clear in those cases 

 in which the young are nourished during their embryonic 

 life by the mother, that, in this way, the young may be 

 rendered immune to a certain extent, and there are instances 

 of this sort recorded, especially in the case of some bacterial 

 diseases. Whether this power can also be transmitted through 

 the egg, in those instances in which the egg itself is set free 

 and development takes place outside the body, has not been 

 shown. In any case, the effect appears not to be a perma- 

 nent one and will wear off when the particular poison no 

 longer acts. It is improbable, therefore, that any permanent 

 contribution to the race could be gained in this way. Adap- 

 tations of this sort, while of the highest importance to the 

 individual, can have produced little direct effect on the evolu- 

 tion of new forms, although it may have been often of para- 

 mount importance to the individuals to be able to adapt 

 themselves, or rather to become able to resist the effect of 

 injurious substances. The important fact in this connection 

 is the wonderful latent power possessed by all animals. So 

 many, and of such different kinds, are the substances to 

 which they may become immune, that it is inconceivable 

 that this property of the organism could ever have been 

 acquired through experience, no matter how probable it may 

 be made to appear that this might have occurred in certain 

 cases of fatal bacterial diseases. And if not, in so many 

 other cases, why invent a special explanation for the few 

 cases ? 



We may defer the general discussion of the role that 

 external factors have played in the adaptation of organisms, 

 until we have examined some of the theories which attribute 

 changes to internal factors. The idea that something innate 

 in the living substance itself has served as the basis for evolu- 



