104 MR. W. BATESON ON [Feb. 2 



another would then be manifest. Eacli would then have its 

 individual history, just as a Fellowship of a College or a Canoury of 

 a Cathedral has an individual history, being handed on from one 

 holder to his successors, some being suppressed and others being 

 founded, but none being merged into a common fund. In other 

 words, the received view of the nature of homologies in teeth 

 assumes that in Variation the individuality of each member of the 

 series is respected. 



The difficulty in applying this principle is notorious, not only in 

 the case of teeth but in all cases of Multiple Parts, such as digits, 

 phalanges, &c. ; and when the actual evidence of Variation is before 

 us, the cause of this difficulty will become apparent enough, for it 

 will be found that though Variation may sometimes respect the 

 individual homologies, yet this is by no means a universal rule ; 

 and, as a matter of fact, in all cases of Multiple Parts, as to the 

 Variation of which any considerable body of evidence has been 

 collected, there are numerous instances of new forms arising in 

 which what may be called the stereotyped or traditional individuality 

 of the members has been superseded. 



The present paper concerns the case of Teeth only, and even of 

 this part of the evidence only a fragment can be given in this 

 abstract, but perhaps it may suffice at least to indicate some of the 

 possibilities which are opened up by the Study of Variation. 



The material examined has consisted chiefly of specimens in the 

 British Museum and the Museums of the College of Surgeons, 

 Leyden, Oxford, and Cambridge, the Paris Museum of Natural 

 History, and several smaller collections. I have to thank the 

 authorities of these several museums for the great kindness I have 

 received from them in the course of my work ; and in particular I 

 must express my indebtedness to Mr. Oldfield Thomas, of the 

 British Museum, for the constant help and advice which he has 

 given me, both as regards the subject of teeth generally, and 

 especially in examining the specimens in the British Museum. 



For various reasons I have for the most part limited myself to 

 the following groups : — Primates (excepting Lemuroidea), Carnivora 

 (CanidaB, Felidse, Viverridse, Mustelidse, and Phocidae), Marsupialia 

 (Phalangeridae, Dasyuridse, Didelphyidse, part of Maeropodidse, &c.). 



Except in the case of teeth which are the terminal members of 

 series, such as the first premolar or the last molar, very few facts of 

 importance concerning the process of reduction in number were 

 seen. From the fact that such cases are generally more or less 

 ambiguous, they must be reserved for fuller treatment. For the 

 present it must suffice to give a brief account of some of the more 

 remarkable phenomena relating to increase in number of teeth. 



The statistics relate to about 2500 skulls belonging to various 

 orders, and the comparative frequency of supernumerary teeth in 

 some of the difterent groups is interesting if only from its para- 

 doxical character. 



Primates. — Of the three larger Anthropoids — Orang, Chim- 



