G2 ORGANIC EVOLUTION — THE FACTORS 



mediate units, which wo may term 'physiological. 

 Thi'ro seems no alternative but to suppose that the 

 chemical units combine into units inunensely more 

 complex than tiiemselves, complex as they are ; and 

 that in each organism, the physiological units produced 

 by this further com])ounding of highly compound 

 atoms, have a more or less distinctive character. We 

 must conclude that in each case, some slight difference 

 of comjiosition in these units, leading to some slight 

 difference in the mutual play of forces, produces a 

 difference in the form wliich the aggregate of tliem 

 assumes." — Prijtri]>l('s of JHology, vol. i. pp. l(S2-'>. 



"... the assumption to wliich we seem driven by 

 the cnscnihlc of the evidence is, that sperm cells and 

 germ cells are essentially nothing more than vehicles, 

 in which are contained small groups of the physiological 

 units in a fit state for obeying their proclivity towards 

 the structural arrangement of the species they belong 

 to." — Ildd. pp. 254-5. 



" If the assumption of a special arrangement of parts 

 ]jy an organism is due to the proclivity of its 

 jjhysiological units towards that arrangement, then 

 the assumption of an arrangement of parts slightly 

 different from that of the si^ecies, implies physiological 

 units slightly unlike those of the species, and these 

 slightly -unlike physiological units, communicated 

 through the medium of siserm cell or germ cell, will 

 tend, in the offspring, to build themselves into a 

 structure similarly diverging from the average of the 

 species." — Und. p. 245. 



" The repair of a wasted tissue may therefore be 

 considered as due to forces analogous to those by which 

 a crystal reproduces its lost apex, when placed in a 

 solution like that from which it was formed. In either 

 case, a mass of units of a given kind shows a power of 

 integrating with itself diffused units of the same kind ; 

 the only difference being that the organic mass of units 

 arranges the different units into special compound 



forms, before integrating them with itself. 



