Whether in the end there will not be a reversion to the judicial and temperate conservative compromise proposed by Flower—and almost everything in this world is based more or less upon compromise—from the headstrong and radical mode of procedure followed by some of the younger zoologists, remains to be seen. Another subject on which Flower insisted very strongly in the work under consideration was the inadvisability of multiplying generic and family divisions in zoology. Here again we may quote his own words. “I do not mean,” he writes, “that with the advancement of knowledge improvements cannot be continually made in the current arrangement of genera. The older groups become so unwieldy by the discovery of new species belonging to them that they must be broken up, if only for the sake of convenience; newly discovered forms which cannot be placed in any of the established genera must have new genera constituted for them, and fuller knowledge of the structure of an animal may necessitate its removal from one genus into another; all these are incidents in the legitimate progress of science. Such alterations should, however, never be made lightly and without a full sense of responsibility for the difficulties which may be occasioned by them, and which often can never be removed. Complete agreement upon this subject can never be expected, as the idea of a _genus_, of an assemblage of animals to which a common generic name may be attached, cannot be defined in words, and only exists in the imagination of the different persons making use of the expression; but there might be no difficulty in coming to some general agreement, if individual zoologists would look at the idea as held by the majority, and would not give way to the impulse to bestow a name wherever there is the slightest opening for doing so.” Here, again, we have golden words, which are unfortunately ignored by a large number of the zoologists and palæontologists of the present day. Most noteworthy, perhaps, in the whole passage, is the emphasis given to the fact that generic groups are but arbitrary creations of the human, and that, far from being natural realities, they are solely and simply formed as matters of convenience, so that their limits are absolutely dependent upon individual or collective opinion.