70 /. H. Powers 



most opposite nature, — an accident rather than an adaptation. It 

 is subject to the widest fluctuations, yet with but a minimum of 

 advantage resulting therefrom either to the individual or to the 

 species. Evidently the power of adaptive response along one line 

 in a species in no way implies such a power along other lines. 

 Adaptive and arbitrary features coexist side by side. 



Before leaving the discussion of the cannibalistic type, I will 

 add a few more facts concerning it. First, I may state that while 

 there is little hypertrophy in the teeth of the upper jaw proper, 

 those of the lower jaw, including those of the splenials, are very 

 greatly enlarged, although the change does not equal that in the 

 palatines. Second, it is interesting to note that, so far as my ob- 

 servation has yet gone, it seems that these cannibalistic individ- 

 uals develop almost exclusively into males. Among the specimens 

 that I have metamorphosed there has occurred but a single fe- 

 male. And among perhaps a half score of wild adults that I 

 have seen, which appeared to me certainly to have resulted from 

 cannibals or semicannibals, not one has been a female. More 

 observations are, however, necessary, especially when the further 

 fact is taken into consideration that, in the writer's vicinity at 

 least, males seem to preponderate as to both numbers and size. 

 Among the sexually mature adults that I have collected, every 

 one of nearly a score of animals which have approached or ex- 

 ceeded the limit recorded for adults of the species (ii inches) 

 has been a male. They outweigh as well as outmeasure the 

 females. 



Finally, I will add that there may possibly be found similar 

 facts of dental variation, due to the same cause, in another species 

 of salamander. At least the careful examination of its habits and 

 teeth in the larval stage would be highly interesting. I refer to 

 Chondrotus tenebrosus, a giant of its genus, parallel in this re- 

 spect to A. tigrinum. Cope records some interesting facts of the 

 larvae of this species. Among others, "The teeth of the larva are 

 stronger than in the adult. They are compressed, double-edged, 

 and acute, having thus a dagger-shape. They can inflict a severe 

 bite. . . I took from the stomach of one of them a larva of its 

 own species of one-third its size." Cope does not seem to have 



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