744 Analyses of Books. [December, 
°f animals are “ susceptible of two or three different methods 
of investigation, which sometimes clash, and lead to opposite 
conclusions. . . . Our answers to these questions will be different, 
accordingly as we lean chiefly on Natural Science, or on Ancient 
History, Literature, or even Language. The purely scientific 
man will judge chiefly by the suitability of soil and climate. If 
he finds a plant flourishing pretty abundantly in Greece or Italy 
now, and knows of no climatic or geologic changes that would 
exclude the idea of its having flourished there 5000 years ago, 
he will at once pronounce it indigenous, and scout the notion of 
its having been imported.” 
. This passage, and especially the words which we have italicised, 
is a complete misconception. The “ purely scientific man ” does 
not “judge chiefly by the suitability of soil and climate.” He 
knows, as one of the most elementary truths in organic geography, 
that soil and climate form merely the exclusive limit to the exist- 
ence of any given animal or plant; i.e., if they are unsuitable 
such animal or plant will be certain not to exist, but it does not 
necessarily flourish where both are suitable. If he were to find, 
e -g., a humming-bird in New Guinea, a bird of paradise in 
Venezuela or I rinidad, a squirrel or a deer in Australia, or a 
kangaroo at the Cape, he would at once pronounce it imported. 
The scientific method of deciding whether a species is indigenous 
or alien in any country is not so simple as Messrs. Helm and 
Stallybrass seem to imagine. We examine, first, whether such 
species stands alone, or is found along with other species of the 
same genus, or of other nearly allied genera. In the latter case 
the probability of its being a rightful native is very strong. We 
next consider whether there are in the country concerned other 
animals, not near of kin to it, but capable of replacing it in the 
economy of Nature. 4 hus the occurrence of carnivorous Mar- 
supialian forms in Tasmania, such as Thylacinus and Dasyurus, 
renders the indigenous existence there of placental Carnivora 
less probable. In like manner the rich development of antelopes 
in the Ethiopian region confirms the non-existence there of true 
deer. Hence if we found an apparently feral deer at the Cape 
we should feel all the more disposed to view it as imported. 
Another consideration is the existence or non-existence of the 
species in question, in some region connected with the country 
undei examination, by lands through which migration could 
have taken place. 1 hus, should a bear be captured in the 
Ethiopian region, we should hold it as having been imported, 
because the regions inhabited by bears are severed from Central 
and South Africa either by the ocean or by wide deserts. 
The last main method of ascertaining whether an animal is 
indigenous in any country or not is the palaeontological. If we 
find its remains in numbers in bone-caves, peat-beds, kitclien- 
middings, &c., and if, on penetrating into older strata, come upon 
traces of allied forms, we feel free to pronounce it indigenous. 
