150 HEREDITY [ap. ii 



somes and body-characters is as yet in its infancy ; 

 and this brief note can only sketch the lines on which 

 modern work seems to support Weismann's hypo- 

 thesis that the chromosomes are the physical basis 

 of inheritance. It will be seen that his suggestion 

 that all the chromosomes are on the whole similar 

 is not confirmed, but the evidence that chromosomes 

 do bear factors for inherited characters is consider- 

 ably stronger than when the idea was first put 

 forward \ 



^ The suggestion referred to in the note on p. 97 must also be 

 borne in mind, that it is not the • factor ' alone which determines the 

 development of a character, but a physiological relation between the 

 factor contained in a chromosome and the surrounding protoplasm. 

 If the latter is altered from any cause, the relation may be changed 

 and the character modified, just as the plants raised from one sample 

 of seed may be modified by growing them in different soils. If, as is 

 quite possible, the relation is a reciprocal one, the factor may in some 

 cases be permanently modified, and there would thus be a mechanism 

 for the transmission of acquired modifications. At present, however, 

 it must be admitted that experiment hardly provides sufiQcient basis 

 for speculations such as these. 



