114 OTHER FACTORS OF EVOLUTION 



by Darwin under the head of " Correlated Variability." ' In 

 reference to this subject he says, "Correlated variation is an 

 important subject for us ; for when one part is modiiied through 

 continued selection, either by man or under nature, other parts of 

 the organisation will be unavoidably modified." This is thoroughly 

 in harmony with what might be expected in accordance with 

 H. Spencer's doctrines. Thus he says': — "if along with a 

 striking change in a flower which the florist contemplates, there 

 go changes all over the plant not obvious to careless observers 

 but visible to him, we must infer that there are everywhere minute 

 differences which even the florist cannot perceive : the whole 

 constitution of the plant has diverged in some measure from the 

 constitution of kindred plants. Every local variation implies a 

 change pervading the entire organism, manifested in concomitant 

 variations everywhere else. ... If so, what becomes of the 

 hypothesis of determinants — the hypothesis that there is a special 

 element in the germ-plasm which results in a special local modifi- 

 cation in the adult animal ? " Yet that the facts are as H. Spencer 

 states he shows by three quotations, one from Darwin and two from 

 Dr. Maxwell Masters. One of the latter refers to the point that 

 among seedling 'stocks' which have not yet flowered, those that will 

 produce double flowers are already distinguishable. Dr. Masters 

 says : — " This separation of the single from the double-flowered 

 plants, M. Chatie tells us is not so difficult as might be supposed. 

 The single stocks, he explains, have deep green leaves (glabrous 

 in certain species), rounded at the top, the heart being in the form 

 of a shuttlecock, and the plant stout and thick-set in its general 

 aspect ; while the plants yielding double flowers have very long 

 leaves of a light green colour, hairy and curled at the edges, the 

 heart consisting of whitish leaves, curved so that they enclose 

 it completely." 



It is certainly true that while such facts as these are wholly 

 incongruous with the hypothesis of determinants, they are in 

 accord with the hypothesis of physiological units. As H. Spencer 

 says, " that a change of structure arising in one part of the 

 organism is accompanied by multitudinous changes of structure 

 in other parts of the organism, is not only congruous with the 

 belief that there exist such constitutional units, but yields it 

 distinct support." 



' " Animals and Plants under Domestication," 1868, Vol. II, Chap. XXV, 

 ' Loc. cit. Vol. II, p. 622. 



