TOOTH -GERMS IN A WALLABY. 



927 



and by Deppendorf (1) ; the latter, however, does not appear 

 to have examined any specimen of llacrojnts. Woodward has 

 furnished the results of his examination of 14 embryos belonging 

 to four species, viz. M. giganteus, M. evgenii, M. bennetti, and 

 M. hrachyu7'us. From the measurements given by him, allowing 

 for the diiferences in size of the adult animals of the different 

 species, our Stage I would appear to be eonsidei"ably younger than 

 any of the embryos w^hich he examined. Before discussing the 

 general considerations arising from our observations, we will 

 proceed to a description of the conditions found in our material. 



Stage I. 



Upper Jaio. — At the anterior extremity of the upper jaw the 

 oral epithelium sinks into the substance of the jaw, forming 

 a broad triangular cellular mass the outline of which is veiy 

 irregular. There are projections of some size extending laterally 

 into the premaxillary region. ISTone of these would, by themselves, 

 suggest tooth vestiges, but the possibility of their being of such a 

 nature is not entirely negatived because, as will be shown in the 

 sequel, similar but more definite structures ai-e to be seen in the 

 lower jaw. The evidence here is, however, too problematical to 

 permit of definite conclusions being drawn. 



Text-fig. 181. 





Oral 





Section sliowing- the tootli-band (X) passing liorizontally inwards and formino 

 tlie anterior part of the tooth-germ J?. 



On either side of the middle line close to the nasal septum is a 

 minute slightly calcified tooth-germ with a dental papilla of 



