7G Enamel in tlie Teeth of an Embryo Edentate 



of the former, he found some with milk teeth and some showing the 

 change to the premanent set. 'J'he last tooth had no predecessor, and 

 the teeth were not changed until the animal had nearly reached the 

 adult stage. On examination of two skulls of Dasypus hyhridus a simi- 

 lar condition was found. A rudimentary incisor was also found in 

 this animal. The milk teeth have been described as two-rooted, but 

 Tomes holds that this appearance is due to the absorption set up by 

 the pressure of the succeeding permanent teeth. 



In 1889, 0. Thomas found in two young specimens of Orycteropus 

 of fourteen and eighteen inches respectively, a complete though rudi- 

 mentary set of milk teeth in each jaw, none of which were in the pre- 

 maxillge. They were all minute, and this fact led him to think it 

 very doubtful that they would ever have cut the gum. Unfortunately 

 his material was limited, and he made no histological investigation, 

 so we know nothing of tlie structure of the enamel organ at this stage. 

 Thomas has also examined specimens of Bradypus, Choloepus, and 

 Dasypus, apparently of a suitable age, and could find no trace of a milk 

 dentition; he says, however, that the possibility still remains that in 

 younger stages uncalcified tooth-buds of such teeth may be present. 

 Tomes and Flower have also examined fu'tal Choloepus and Bradypus 

 and have found no trace of any milk dentition. 



In 1892, Rose (92% p. 507) observed in an embryo of Myrmecophaga 

 (Udactyla 20 cm. long, at the point of the jaw, where in other cases the 

 tooth-buds are connected with the mouth epithelium, a row of excep- 

 tionally high papilla?. He thinks that very probal^ly in younger, stages 

 the tooth-buds were formed at this place but were not further developed. 

 In the same year, in an embryo of 7.G cm. of Manis tricuspis and one of 

 ]\f. javanica of 9 cm., Eose ° found well defined dental folds in both upper 

 and lower jaws, and in the lower jaws rudimentary club-shaped tooth- 

 l)uds. He has shown by examination of older specimens that they sub- 

 sequently disappear. 



The only work that has been done on the teeth of the armadillo since 

 that of Tomes has been done by Eose and by Ballowitz who worked at 

 the same time but independently of each other. 



In 1892, Eose examined two embryos, one of Dasypus novemcinctus 

 of 7 cm. and one of D. hyhridus of 6 cm. In the first-named embryo he 

 found an enamel organ composed of an inner and an outer epithelial 

 layer and a well developed stellate reticulum. He did not describe any 



2 The mounted slides of these embryos had been furnished by Max Weber {'91) who 

 had not found any indicatiou of the dental folds. 



