30 FRANK E. BEDDARD 



multicuspidate teeth, or, on the other hand, show by this 

 arrangement the speciahzation of sets of separate cusps — 

 a promise of separate multicuspidate teeth in the future. I 

 may remark, however, that these connexions between successive 

 teeth may possibly be related to the fact that in the adult the 

 individual teeth are connected by a tough gum which comes 

 away with them when they are forcibly removed from the bony 

 trough in which they lie. 



Ebsumb. 



As to the facts contained in the above pages they are really 

 summed up in the illustrations which accompany the letterpress. 



There are tooth germs from end to end of both upper and 

 lower jaws, except at the posterior end of the series, where the 

 dental lamina is not specialized in the upper jaw for some 

 little distance. The teeth, in fact, are developed from behind 

 forwards. 



The dental lamina extends into the subjacent mesoderm at 

 absolutely right angles to the horizontal plane of the head. 

 The dentine papilla is represented only by a condensation of 

 nuclei in the mesoderm ; it does not yet extend into the cavity 

 surrounding the enamel organ. 



The tooth rudiments of the lower jaw are borne upon a 

 shorter dental lamina than those of the upper jaw. They 

 consist of the dental lamina which is prolonged beyond the tooth 

 germ as a ' residual lamina ' and of the tooth germ arising from 

 the lingual surface of the lamina. 



The tooth rudiments of the upper jaw are borne upon a 

 longer dental lamina than those of the lower jaw. They 

 consist of the dental lamina which is prolonged beyond the 

 tooth germ as a ' residual lamina ' ; but this consists, not of 

 a continuous lamina as in the lower jaw, but of a series of 

 processes one to each of the successive tooth germs. In 

 addition to these there is always a second outgrowth of the 

 dental lamina on the labial side (sometimes doubled) lying nearer 

 to the origin of the dental lamina, which do not form a con- 

 tinuous lamina but are separate outgrowths corresponding 



