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 de- 

 mand it. 



A judicious scepticism seems to me 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 evolu- 

 tion 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 discrimina- 

 tion 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 me to be unscientific as well as unphi- 

 losophical. 



If, as I believe, so many similar forms have arisen in mutual in- 

 dependence, 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, we 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. 



On 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. 



We 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 Lemuroidea. 



