728 



Anlage of a Reptile. Already Lkche pointed out tliis agieenient of 

 tlie teeth-band apparatus witli the tooth-gei-ins between Marsupials 

 and Reptiles foe Myrmecobius (Morph. Jalirb. XX j). 1J8). This 

 author says in the place referred to: "dasz die erhaltenen Bilder in 

 Bezug auf die Beziehungen der Sciinielzleiste des rudiinentiiren 

 Zahns zur Leiste der persistierenden eben so selir von den bei allen 

 übrigen Sangethieren vorkoinmenden Befunden abweiciien, wie sie 

 an Zustiinde bei manchen Repiilien erinnern" (that the obtained 

 pictures in regard to the relations of tlie border of the teethband 

 of the rudimentary tooth to liie teethband of tlie permanent teeth 

 differ as much from what is fouiid with mammals as they remind 

 us of the conditions with many Reptiles). 



As will be seen from fig. 3, of the exostichical teeth only three 

 develop, namely those numbered 3, 6, and 7. Especially the meaning 

 of tooth 3 and 7 is important for our further discussion and therefore 

 it is necessary that its exostichical nature is definitely proved. So 

 in fig. 5 some fifteen successive sections are given tiirough the region 

 of the teeth-band, enclosed in fig. 2 between the lines A and B. 



In this region lies also tlie posterior end of the endostichical tooth 

 a, visible in the sections a, b, and c as a terminal thickening of the 

 dental lamina. Then follows the exostichical tooth 2, already furnished 

 with a dentine cap, but otherwise rudimentary, sketched in sections 

 b-f. That this tooth is formed from the teeth-band not terminally 

 but |)arietally is clearly seen. Next comes the endostichical tooth b, 

 the Anlage of which may be followed in the sections f-p as the 

 already terminally invaginated thickening of the dental lamina. But 

 before this Anlage is completed that of the exostichical tooth 3 appears. 

 That also this tooth is connected with the teeth-band not terminally 

 but parietally like the tooth 2 and consequently belongs to the 

 exostichos, is proved beyond doubt by the pictures. As an additional 

 proof the Anlage of tooth /> and tooth 3 at a younger stage of 

 development is given in fig. 6. This is a reproduction of Wilson 

 and Hill's fig. 34. In my opinion there can be no doubt as to the 

 exostichical nature of tooth 3 in Perameles. That so much stress is 



