DISCONTINUITY OF SPECIES II 
tude, are all capable of changing the general appear- 
ance of a plant so as to render it scarcely recognisable. 
Fortunately, in the case of the higher plants, the 
floral organs, which are the ones chiefly made use of 
for purposes of specific discrimination, are very little 
liable to modification by external conditions; but 
in the corals a similarly stable set of organs does 
not appear to have been discovered. It seems, there- 
fore, hardly fair to regard the example of the corals 
as affording an established exception to what we 
must look upon as the general rule—namely, that 
species are on the whole definite and discontinuous 
groups. 
As a tule, then, the species riddle presents itself 
definitely as the problem of the existence of a series 
of discontinuous groups of creatures, sharply marked 
off the one from the other, and often, too, existing 
among surroundings which afford no corresponding 
discontinuity, though each is well enough fitted for 
the life which it has to lead. 
The problem which we have to face has been 
enunciated by Bateson in the form of the two following 
propositions : 
‘1. The forms of living things are various, and on 
the whole are discontinuous or specific. 
‘2. The specific forms on the whole fit the places 
they have to live in. 
‘How,’ he continues, ‘have these discontinuous 
forms been brought into existence, and how is it they 
are thus adapted ? This is the question the naturalist 
is to answer. To answer it completely he must find 
