Origin and Development of the Composites. 77 
generally recognised as not uncommon (cp. 10 and 40), and con¬ 
vergence, epharmonic or otherwise, which is also becoming 
recognised as an important point in evolution (cp. 10, 57 and X, 
15 and X, 69, Vol. II, p. 115) have analogues here also. Con¬ 
vergence may be noted in Radium P and the end-products of the 
Radium C l and Actinium D lines, and also in the similarity of 
the end-products of all the disintegration series in both Figs. 41 
and 42. Parallel evolution and polyphyly may be noted in the 
identity of the end-products of the last two lines in Fig. 41 and 
and of the Thorium C' and Thorium D lines (Fig. 42). Allotropic 
modifications, such as occur in sulphur, are unknown in the 
radio-active elements so that there is no analogy here for tetra- 
ploid mutations, although these find their analogue amongst the 
other elements. 
Thorium 
JP'6 ‘ lO^YCAV, 
fcsOJHORIUn I 
7 9 vc *PS 
tt[$OWOQIUH n 
Q- 9 houbs 
Radio-thorium 
S9l rCAKS 
Thorium A 
5-25 days 
Emanation 
Thorium A 
j O iO secs. 
Thobium B 
/$-4 HOUQS 
THOBiun C 
Thorium C/ 
/O'" SIC. 
End 
The radio-active analogy 
holds good, therefore, for most 
of the details of orthogenetic 
saltation; it fails, however, to 
be complete for evolution be¬ 
cause external circumstances 
have apparently no effect on 
the course of the disintegration 
and the form of the constituent 
members of the uranium and 
actinium series. This is more 
or less true for orthogenetic 
saltation alone but epharmosis 
finds no analogue in radio¬ 
activity. Such an analogue 
does, however, occur in crys¬ 
tallisation and other chemical 
phenomena which simulate the 
processes of life. 
Fig. 42. Thorium Disintegration Series. 
“ The truth is that adaptation explains the sinuosities of the 
movement of evolution, but not its general directions, still less 
the movement itself ” (Bergson, op. cit. , p. 107). Elsewhere this 
philosopher compares life and evolution to a river—“ The move¬ 
ment of the stream is distinct from the river bed, although it must 
adopt its winding course,” (op. cit., p. 284). Dendy (35) uses the 
