6 io Willis. — The Origin of Species by Large , rather than by 
It was, moreover, shown that no use-value could conceivably be put to 
the two most important characters by which this Coleus was distinguished 
from other species of the genus—the equally toothed calyx and the different 
type of inflorescence. Even in the minor characters of difference (cf. ‘ Age 
and Areap. 152, or below, p. 620) it was very difficult, if not usually 
impossible, to point out any way in which they could be of service or dis¬ 
service. It was then shown that in the case of the two chief, and of some 
of the minor characters, evolution from the characters of the other Colei, or 
from some intermediate type, by gradual variation, was impossible, on 
account of the impassable gaps in the transition, only to be passed by sudden 
and rather ‘large’ variation. In the case of the calyx, for example, all 
sepals behave alike in ordinary variation, and a calyx of one large and four 
small sepals could never vary gradually in the direction of one with five 
equal sepals. 
Further than this, evolution by Natural Selection demands variation in 
the same direction in large numbers, to avoid intercrossing, and on the 
summit of Ritigala there is not sufficient room for four local species to have 
evolved in this way—a Coleus on rocky spots, a Trichomanes in shady places, 
a Bulbophylhim living epiphytically, and a Cypertis in open grassy places, to 
say nothing of the endemic varieties. Finally, the Coleus was accompanied 
at the summit by its most nearly related species, C. barbatus (common in 
tropical Asia and Africa), living in similar spots, and just as common. This 
latter species is, upon my view, the probable ancestor of the former. 
Many similar cases were then brought up from the floras of Ceylon and 
other countries to show that endemic species as a general rule were sepa¬ 
rated from the ‘ wides ’ that accompanied them (and were usually closely 
related) by differences which could only be passed over by mutations, often 
‘ large’. To make a few quotations : ‘ Ranunculus sagittifolius , confined to 
the high mountain region about Nuwara Eliya, differs widely from the only 
other Ceylon buttercup, R. Wallichianus (South Indian also), which occurs 
side by side with it, though in drier and sunnier places, but is closely allied to 
R. reniformis of the mountains of the Western Indian Peninsula, differing 
mainly in the petals, which are five in the Ceylon species, 12 to 15 in the 
Indian one. . . . Are we to suppose the conditions of life so different in the 
Ceylon and Indian mountains that a five-petalled flower will suit the one, 
a twelve-petalled the other ? Or how is the one to pass into the other, or 
both to arise from a common ancestor, except by discontinuous variation?’ 
‘ Can it be supposed that the simple obovate-lanceolate leaf of Acrotrema 
intermedium fits it for the Kitulgala district, while the pinnate leaf with 
linear-lanceolate segments of A. Thwaitesii fits that species for the Dolos- 
bage district, but a few miles away, a trifle higher up, and in a similar 
climate? ... A. lyratum , characterized by very long peduncles, is found 
only on the summit of Nillowekanda, an isolated precipitous rock ... is it 
