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Show 510 MR. ST. G. MIVART ON THE LEMURS. [May 20, are really two in origin, it is not on that account they should be divided into two orders, but for convenience, should convenience demand it. A judicious scepticism seems to m e to be somewhat needed at the present moment. The considerations here advanced are by no means intended to support the assertion that views as to genetic affinity are mere dreams. Far from so believing, I conceive the theory of evolution to be probably true; and if so, real genetic affinity must exist, and when it can be securely detected must be most important. But the response of organization to need being such as it is (structure and function manifesting themselves so simultaneously), the discrimination between genetic and adaptive families must long, if not ever, continue a work of extreme delicacy and difficulty. The hasty way in which a few detected (often superficial) resemblances have of late, from time to time, been made to do duty as sufficient evidence of affinity and descent, seems to m e to be unscientific as well as unphi-losophical. If, as I believe, so many similar forms have arisen in mutual independence, then the affinities of the animal kingdom, or even of the Mammalian class, can never be represented by the symbol of a tree. Rather, I believe, w e should conceive the existence of a grove of trees, closely approximated, greatly differing in age and size, with their branches interlaced in a most complex entanglement. O n this view, the classification of existing and extinct animals can never, at any future time, be constructed on a purely genetic basis; but surely it need not therefore be a merely arbitrary and artificial system. If we find that a group of animals can be defined not by one character, but by the coexistence of numerous specialities of structure, such group must certainly be deemed a natural one, since order pervades the organic as well as the inorganic kingdoms of nature. W e can grasp the idea of " serial homology," and understand what is a " homotype ;" and though homotypes as such have only a mental existence, the characters whence the conception is derived are actual real existences. So with a species, a genus, a family, or an order, though these entities exist as such only in the mind, the phenomena whence we derive such conceptions exist actually in rerum natura. It does not follow, therefore, that zoological groups need repose upon no philosophical conception if they cannot rest upon a genetic one. The group Primates can, as has been said, be clearly defined and distinctly conceived, however few or many may have been its sources of origin. I venture, then, still to maintain that the order Primates is a natural, definite, and convenient one, and that, to say the least, it would be a questionable step to raise to a higher value that which I think may be best designated as the suborder L E M U R O I D E A . |