Ridley. — On Endemism and the Mutation Theory. 553 
entirely prevented the propagation of the plant. The bug appeared to me 
to be identical with a species which attacked the Cotton plant in the same 
manner, and was one of the two species which prevented our cultivation of 
Cotton in the Malay Peninsula. I will add that a large part of the Lantana 
which was destroyed throughout the island was destroyed by the extensive 
planting of Para Rubber in Singapore, whereby the lands which after the 
Chinese had abandoned the cultivation of Gambir and Pepper there had been 
largely covered with Lantana were again cleared of weeds and bushes, includ- 
ing the Lantana. The action of man in destroying species I will refer to later. 
The action of enemies, whether insects, fungi, or bacteria, in the destruc- 
tion of a species in a natural state has not yet received that attention of field 
naturalists which the subject requires ; but every tropical agriculturist knows 
that an insect or fungus which commonly lives on one particular plant may 
adapt itself so as to attack another allied plant, and, if the latter grows in 
abundance in any area, may practically exterminate it. 
An excellent example of the destruction of a species completely within 
a very limited space of time is furnished by the extermination of the two 
rats of Christmas Island. 
This island was first visited by any naturalist in 1886, when the Egeria , 
with Mr. Lister as naturalist, visited the island. At that time the island 
swarmed with both species of rats, especially Mns Macleari , the white-tailed 
rat, of which, judging by accounts, there must have been millions. In 1904 
Dr. Hanitsch and I visited the island to collect the flora and fauna, and 
though we went far into the forest and set traps for rats, not one of either 
species was to be met with. On inquiring of the residents on the island, we 
were informed that the white-tailed rats had totally disappeared, and the 
last one that was seen was rambling about apparently very sick in the 
neighbourhood of the settlement. What had happened ? The only probable 
solution was that the destruction was caused by the introduction of the 
common brown rat ; not from this animal having eaten up the food of the 
white-tailed rat, for the rat’s food, the fruits of the trees in the island 
forests, lay untouched on the ground in abundance, but in all probability 
from the introduction of some bacterium (possibly the plague) by the 
stranger. The brown rat itself had not spread over the island to any extent, 
and mainly confined itself to the neighbourhood of the settlement. 
A very similar case appears to have occurred also in the island of 
Fernando de Noronha, where, when this island was discovered, there was 
great abundance of a large rodent described by Mazarredo in 1774 as the paca 
or mulita of Buenos Aires. This animal has apparently utterly disappeared, 
for in my expedition to that island in 1887 we were unable to discover any 
trace of it, nor did any of the residents know of its existence. If such 
destructions of an animal species may occur in so short a time, why should 
not the same thing occur in plants ? 
