58 Soitthern Cross. 



again couti'il)utcs largely. On the contrary, tberc is no instance of a 



double-rooted p.m. — , and of p.m. - it may be said tbat in all 



cases where this tooth was found in situ it also was single-rooted. 

 In a single case (No. 4), where all the teeth had been removed from 

 the skull, and could not be certainly identified, I suspect it to have 

 been double-rooted. 



(XII.) Besides variation in number and shape there is also 

 variation in size. The teeth of No. 807 are abnormally small ; those 

 of No. 3 abnormally massive, and crowded together in the jaw, 



(XIII.) Further, the size of the incisors is conspicuously variable, 

 as exhibited by the large incisors of No. 324& and the small ones 

 of No. 897. 



Having thus described the variations to which the teeth of the 

 known specimens of Ommatojyhoca are subject, it is time to turn to 

 what has been written on the subject by Mr. Bateson and Dr. 

 Kiikenthal. In fairness to these writers it should be at once stated 

 that Mr. Bateson's remarks were based upon an examination of only 

 two skulls — those brought home by Eoss, — while, so far as 1 know. 

 Dr. Kiikenthal never had an opportunity of seeing the actual 

 specimens, but based his conclusions on mere descriptions and upon 

 Mr. Bateson's arguments. It will not then appear surprising, if I 

 find myself, after the advantages of examining no less than eight 

 skulls, unable to agree with all that has been written on the subject. 



To deal first with Mr. Bateson. That naturalist has found in the 

 variations of skull No. 3246 the material for a highly ingenious 

 paper, wherein he has used them in conjunction with other like 

 variations as a ram wherewith to batter the prevailing views on the 

 homologies of mammalian teeth. 



As the result of an examination of great numbers of skulls of the 

 Primates, Carnivora and Marsupialia, he finds that in many 

 examples of various genera and species " reduplication of teeth may 

 occur in such a way that a tooth which is usually single may be 

 represented by two teeth, and that the two teeth thus formed may 

 either (1) both take place in the ordinary series, or (2) may stand 

 externally and internally respectively." 



The prevailing hypothesis, as Mr. Bateson points out, necessarily 

 " involves a definite conception of the mode in which variation 

 works," and, further, that " in variation the individuality of each 

 member of the series is respected." 



But, as in the case also with otlicr multiple parts, sucli as digits 

 and phalanges, the diiiiculty in applying this principle and in 



