Origin and Development of the Composites. 75 
and is closely akin to the action of isolation and epharmosis. 
Of these theories which attempt to explain more or less the same 
phenomena,epharmosis is supported by the most conclusive evidence. 
Even Andrews (X, 3-4), who is quoted by Guppy in support of 
his theory writes (X, 4, p. 536) of “ an organic response to 
severer conditions of climate and to a greater poverty and 
porosity of soil.” 
Fountain’s opinion is interesting as that of an amateur, who 
knew little of botany and less of the literature of epharmosis. 
He writes (16, p. 227) “In fact, the peccary, as all, or nearly all, 
other animals bears out my theory that species (that is 
variations from original types) are the outcome of locality, and 
not of ‘ natural’ or any other kind of ‘selection.’” 
Conclusions. 
The action of orthogenetic saltation is discussed by Davenport 
(IV, 25), whose chief point is that internal laws give a breaking up 
of the complex germ plasm. He gives the origin of radium as an 
analogy but does not develop the analogy in the detail which it 
deserves. 
Considering the “evolution” of the Uranium-Actinium Series 
(Fig. 41), 1 it will be noticed that, whereas some of the elements (to 
be regarded as species) have a long life, others are very unstable and 
exist only for a short time. Orthogenesis finds its analogue in the 
straight series from Uranium 1 to Radium C (Fig. 41) and from 
Thorium to Thorium C (Fig. 42), each step in the series being 
dependent on the preceding steps. Divergence of types finds its 
analogue in the splitting of Radium C (Fig. 41) and of Thorium C 
(Fig. 42) to give two distinct series each. The irreversibility of 
evolution (cf. 41a) is the same as that of the disintegration series. 
Both infinitesimal variation and mutation have analogues, the 
former in those cases where the imponderable particle is thrown 
off, giving a new form and the latter in those cases where a 
perceptible explosion takes place and the helium particle is 
thrown off. It will be noticed that it is always by loss of something 
that a “ mutant ” arises. It is perhaps stretching the analogy too far 
to extend it to cytology, the first case corresponding to the loss 
of one gene from a chromosome and the second to the observed loss 
1 I am indebted to Dr. J. F. Spencer for the details given in Figs. 41-42 
Th? times given are half life-periods, or the time taken for 50% of any given 
quantity of an element to change into the next of the series. The numbers within 
the circles are the atomic weights. The (3 particle is imponderable and the <v 
particle (helium) has an atomic weight of 4. The dotted lines indicate probable 
but unconfirmed lines of development. 
