1873.] MR. ST. G. MIVART ON THE LEMURS. 509 



tendency of the Simiadce to develop cheek-pouches and ischiatic 

 callosities, and the constant absence of any manifestation of such 

 tendencies in the Cebidce ; (5) the different general form and habit 

 which the two groups present. 



All these characters taken together seem to me to make it highly 

 probable that the Cebidce and Simiadce are no diverging offshoots 

 from some common Ape-parent, but that they have arisen in an in- 

 dependence as complete as that between the origin of either of them 

 and the origin of the Lemuroids or Carnivores. 



I need hardly add that I do not consider that such a fact of origin, 

 could it be proved, would constitute any valid reason for raising the 

 two Ape-groups into two distinct orders. 



Those, however, who take this view as to their origin, and who, at 

 the same time, would make the Lemuroids an order on genetic 

 grounds, should be logically compelled to take the same step with 

 regard to the Simiadce and Cebidce. 



It will be asked, But can it be possible that two genera which 

 possess so many points in common as Cebus and Cercopithecus have 

 come to resemble each other independently 1 



I confess. I cannot see any reason why they should not have so 

 come. We have abundant examples of separate points of resemblance 

 which have independently arisen. Amongst such maybe mentioned 

 the flying Squirrels and the flying Phalangers ; the canines and 

 premolars of Canis and Thylacinus, the grinders of Perameles and 

 Urotrichm, and, as before mentioned, the cervical vertebrse of Au- 

 ckenia and Myrmecophaga. 



As to the extremities, Didelphys and Phalangista, and, according 

 to many, the Lemuroids also, show how an opposable inner digit may 

 exist independently of inheritance. 



But if some naturalists are disposed to admit that the common 

 origin of the Cebidce and Simiadce may be very doubtful, can they 

 be even sure that Cercopithecus and Hylobates can claim a common 

 Ape-ancestor ? 



In proposing these questions I am far from venturing to positively 

 affirm the genetic distinctness of different Apes ; my object is to ob- 

 tain a decision as to the third question — namely, what is the more 

 prudent course to follow as to the classification of such forms as may 

 seem to be probably or possibly distinct in their origin ? 



I would urge that the more prudent course is to give to genetic 

 considerations a decidedly subordinate place in questions of classifi- 

 cation — and this on two grounds. 



If any two groups of animals can easily be joined together in a 

 larger aggregation capable of distinct definition by numerous cha- 

 racters, easily discernible and drawn from structures important in 

 the economy of life, then I submit such groups should be so joined, 

 provided they do not constitute a whole inconvenient and unmanage- 

 able from the number of its subdivisions. 



As to the Cebidce and Simiadce, then, I say, if they are really one 

 in origin, it is not on that account they should be kept united in 

 the same order ; and, similarly, if the Anthropoidea and Lemuroidea 



