More than a thousand languages exist as “living” languages, no one of which is intelligible to the speakers of another. These separate languages, however, are obviously divisible into families—all the members of each family being more or less closely allied, while members of different families do not present any such evidence of genetic affinity. The test of genetic affinity is resemblance in structure, grammar, and roots. Judged by this test, the thousand or more living languages are classified by Professor Friedrich Müller under “about one hundred families.”[148] Therefore, again to borrow biological terms, we may say that there are about one thousand existing “species” of language, which fall into about one hundred “genera”—all the species in each genus being undoubtedly connected by the ties of genetic affinity. But besides these species and genera of language, there are what may be termed “orders”—or much larger divisions, each comprising many of the genera. By philologists these orders are usually called “groups,” and whether or not there is any genetic relation among them is still an unsettled question. From the very earliest days of true linguistic research, three of these groups have been recognized, and called respectively, (1) the Isolating, (2) the Agglutinative, and (3) the Inflectional. I will first explain the meaning which these names are intended to bear, and then proceed to consider the results of more recent research upon the question of their phylogeny. In the _Isolating_ forms of language every word stands by itself, without being capable of inflectional change for purposes of grammatical construction, and without admitting of much assistance for such purposes from demonstrative elements, or modifying constants. Languages of this kind are often called _Monosyllabic_, from the fact that the isolated words usually occur in the form of single syllables. They have also been called _Radical_, from the resemblance which their monosyllabic and isolated words present to the primitive roots of languages of other types—roots which, as already indicated, have been unearthed by the labours of the comparative philologist. Thus, upon the whole, the best idea of an isolating language may be gained by comparing it with the “nursery-language” of our own children, who naturally express themselves, when first beginning to speak, by using monosyllabic and isolated words, which further resemble the languages in question by not clearly distinguishing between what we understand as “parts of speech.” For in isolating tongues such variations of grammatical meaning as the words are capable of conveying are mainly produced, either by differences of intonation, or by changing the positions which words occupy in a sentence. Of course these expedients obtain more or less in languages of both the other types; but in the isolating group they have been wrought up into a much greater variety