For example, the earliest classification of the animal kingdom with which we are acquainted, grouped together, under the common designation of “creeping things,” articulata, mollusca, reptiles, amphibia, and even certain mammals, such as weasels, &c. Here, it is evident, the classification reposed only on the very superficial resemblances which are exhibited by these various creatures in their modes of locomotion. As yet conceptual thought had not been directed to the anatomy of animals; and, therefore, when it undertook a classification of animals, in the first instance it went no further than to note the most obvious differences as to external form and movement. In other words, this earliest conceptual classification was little more than the verbal statement of a receptual classification. But when the science of comparative anatomy was inaugurated by the Greeks, a much more conceptual classification of animals emerged—although the importance of anything like a systematic arrangement of the animal kingdom as a whole was so little appreciated that it does not appear to have been attempted, even by Aristotle. For, marvellous as is the advance of conceptual grouping here displayed by him, he confined himself to drawing anatomical comparisons between one group of animals and another; he neither had any idea of group subordinate to group which afterwards constituted the leading principle of taxonomic research, nor does he anywhere give a tabular statement of his own results, such as he could scarcely have failed to give had he appreciated the importance of classifying the animal kingdom as a systematic whole. Lastly, since the time of Ray the best thought of the best naturalists has been bestowed upon this work, with the result that conceptual ideation has continuously ascended through wider and wider generalizations, or generalizations more and more chastened by the intentional and combined accumulations of knowledge. How enormous, then, is the contrast between the first simple attempt at classification as made by the early Jews, and the elaborate body of abstract thought which is presented by the taxonomic science of to-day.