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THE AMERICAN NATURALIST 



[Vol. XL VI 



remaining cases which might [otherwise] be considered normal salta- 

 tions or reversions may actually be teratologic, but disguised by 

 homoeosis; all of the possibly significant cases (such as the supernu- 

 merary molars) are thereby placed under suspicion. Setting aside this 

 suspicion the minority of the " significant " cases in teeth and feet may 

 be said to afford evidence of the meristic variability of vestigial and 

 rudimentary structures. Bateson's statement that such variability is 

 related not to non-functionalism but to terminal position in a series 

 appears to me directly in conflict with his [Bateson's] own evidence, 

 as it certainly is with all my experience. This accords with commonly 

 observed data in paleontology, for no paleontologist would question 

 that vestigial teeth or bones are apt to [finally] disappear by " discon- 

 tinuous" evolution. As to the appearance by saltatory evolution of 

 new and primarily functional parts in teeth or feet, I know of no ade- 

 quate paleontolooic evidence in its favor. It is either demonstrably 

 false or decidedly improbable. In the cases of supernumerary teeth 

 {Otocyon myrmecobius, Cetacea, etc.) saltatory evolution may be re- 

 garded as reasonable in default of any paleontologic evidence to the 

 contrary. Meristic or numerical evolution in fully functional verte- 

 bra is intrinsically probable as the only method of evolutionary 

 change. 



The fact that so many cases of supernumerary teeth are associated 

 with asymmetry throws doubt on the significance of all such cases; 

 asymmetric variations and those occurring only in upper or only in 

 lower teeth have no analogy in paleontology; such cases as occur ab- 

 normally are recognized as of a different and non-significant class than 

 normal evolutionary changes. 



A summary of Matthew's report is as follows: 

 Bate son cites 323 cases of discontinuity in vertebrae, 

 teeth and skull. Of these 286 are abnormal, or teratolog- 

 ical, or reversional, and have absolutely no significance 

 in evolution; ten cases of supernumerary (or fourth 

 molar) teeth are possibly significant because among the 

 mammals there are a few genera with fourth molars 

 which may possibly have arisen by saltation. There re- 

 main only thirty-seven cases which may be ranked as 

 " probably significant," and these are the meristic addi- 

 tions or reductions of vertebrae in the spinal column, 

 significant because of the well-known variations in the 

 vertebral formulae of different mammals, and secondly 

 because vertebrae can be added or subtracted only dis- 

 continuously. 



