50 VARIATION 



5. Dog with lower jaw and teeth normal, but with upper canines imper- 

 fectly divided. The division was more complete on the right side, forming 

 practically two canines standing in line with the regular teeth. 



6. Dog with first premolar in right side of upper jaw doubled, both teeth 

 being normal in shape, the anterior somewhat the larger. 



FIG. 7. Merism in teeth : canines partially divided. After Bateson 



7. Dog with an extra premolar on both sides above and below, the denti- 

 tion formula being p ~~ . 



8. Sledge dog : " All teeth normal, except left upper p 2 . This tooth nor- 

 mally has two roots. Here it is represented by two teeth, each having one 

 root." 



9. Absence of first premolar frequently quite common in Eskimo dogs, 

 suggesting a breed peculiarity. 



10. Among domestic dogs supernumerary molars were found in twenty- 

 eight cases out of 345 skulls examined, as follows, 1 the normal dentition of 

 the dog as to molars being two above and three below (m 2). 



tn 9 on both sides and m* on one side I case 



m* on both sides 2 cases 



#z 8 on one side 9 cases 



w 8 and w 4 on one side only 2 cases 



m 4 on both sides 6 cases 



m* on one side only 8 cases 



This strongly suggests the formula wf, which is that of 

 Otocyon (Lalandes dog) and of the fossil Amphicyon, the sup- 

 posed doglike progenitor of the bears. It calls to mind the 

 further remarkable facts that Otocyon itself varies from m\ 

 to m | and that it is the only mammal outside the marsupials 



1 Bateson, Materials, etc., p. 220. 



