TOOTH-GENESIS IN THE CANIDiE. 457 



If, however, my aforementioned conclusions with regard to 

 pm.^ be accepted, it must I think be concluded that the molars 

 belong also to the permanent series. If the molar region of a 

 foetal pup be examined at about the seventh week, the tooth will 

 be seen developing, and there is a slight trace of the dental 

 lamina on its labial side. At a later period, after birth, this 

 labial downgrowth has disappeared, the tooth itself is well de- 

 veloped, and, in addition, there is a strong downgrowth of the 

 dental lamina on the lingual side. Here then, again, are evidences 

 of thjee dentitions, from the central one of which the molars 

 develop ; and, consequently, I regard them as belonging to the 

 permanent series. 



Again, it is a very curious but well-known fact that in the 

 upper jaw of the Dog the characters ot" the last deciduous pre- 

 molar are similar to those of the first true molar, and those of 

 the penultimate deciduous premolar to those of the permanent 

 carnassial ; that is to say, that the specialized carnassial tooth is 

 preceded in position by a tooth molariform in character. 



If the last deciduous premolar of a Dog, about three days old, 

 be examined in serial sections, we find a condition identical with 

 that alrea^dy described in the foetal condition of the true molar 

 region : namely, a labial downgrowth of the dental lamina, a 

 central one from which this deciduous tooth is developed, and a 

 lingual downgruwth (27). This last downgrowth ultimately dis- 

 appears, the permanent carnassial developing anieriorly and 

 altogether independently of it. 



The conditions in the case of this last deciduous premolar 

 being the same as in the case of the true molars, the conclusion 

 must be the same ; that is to say, that this deciduous tooth 

 belongs to the same series as the true molars, which it resembles 

 in characters, and that its successor m position, the permanent 

 carnassial tooth, is not its true morphological successor, that 

 successor not developing *. 



There here arises the question, to what dentition is the per- 

 manent carnassial to be referred? Does it belong to ttie per- 

 manent series ; or is it, owing to its great development, a 

 delayed milk-tooth, as my friend Mr. M. E. Woodward has 

 suggested? 



In a seven weeks' foetal pup we find the developing tooth (fig. 5, 



* This is in agreement with the conclusion by M. F. Woodward for the 

 Insectivora, in Brit. Assoc. Eeports, Ipswich, 1895, p. 736. 



