340 Willis .— The Sources and Distribution of the 
(2) That I have not allowed enough for other factors that determine 
distribution. 
(3) That the bulk of endemic species are ‘ relicts ’ and not new appear¬ 
ances, i. e. that they are in general older than the wides that are mingled 
with them ; ‘ very many endemics owe their limited distribution to the 
circumstance that they are remnants of comparatively unsuccessful types 
which have been exterminated elsewhere, and which even in these isolated 
floras are waging a losing fight against more vigorous and adaptable 
new-comers.’ 
(4) That trees and shrubs are in general older than herbs. 
(5) That age tends to the disappearance of old species. He ‘ regards 
isolation as a factor which tends not only to develop new species, but also 
to modify and extinguish old ones; and hence looks upon species in Ceylon 
and New Zealand which still maintain specific identity with their co-types 
on the mainland as the newest arrivals rather than as the most ancient 
members of the flora’. 
(6) That age and area fails to explain the distribution of the New 
Zealand flora. 
(7) Certain minor criticisms near bottom of p. 214. 
I must begin by pointing out one or two instances in his papers where 
Dr. Sinnott shows that he has not quite clearly grasped the exact meaning 
of my work—no doubt on account of my imperfect presentation of it. In 
the first paragraph of his paper (11) he quotes my hypothesis without the 
very important proviso that it be only applied in cases of about twenty 
allied species, and then goes on to argue as if it were intended to apply in 
individual cases. He states that ‘ a highly specialized form, occupying 
a relatively narrow ecological niche, may in reality be much older than one 
which from its greater adaptability under diverse environments is able to 
thrive over a wider area’. Perfectly true, but it is in the highest degree 
unlikely that he would find twenty allied forms, or even a whole genus of 
more than five or six species, living in the same ecological niche, and in the 
rare cases where this does occur, one would not reason as to age. 
On p. 215 he quotes the facts upon which I have founded my hypothesis, 
but omits the very important detail that not only is the area occupied by 
the wides greater, but they show their maximum number occupying the 
largest area, and the numbers are graduated down from this. The endemics, 
on the other hand, usually show the maximum number on the smallest area, 
and the numbers are graduated in the reverse direction, unless, as in the 
case of the species endemic to New Zealand and the islands, or the fern 
endemics, they are also very old. He likewise omits the important detail, 
which was what led me first to form the hypothesis, that the species of 
Ceylon and Peninsular India (and the same is true of those of New Zealand 
and islands) were on the whole intermediate in area occupied between those 
