90 MICROSCOPIC ANATOMY OF THE TEETH 



have been hitherto described in the Sparidae, as the species 

 examined had always been S. ovis, in which there is no 

 penetration by tubes from the dentine. Another species 

 of Sargus, S. vulgaris, also shows penetration by dentinal 

 tubes, but they only penetrate for a short distance, ter- 

 minating at the densely calcified layer of prisms above 

 described. 



We see, therefore, that in the same genus (Sargina) there 

 is a very complete penetration by both systems of tubes 

 in Sargus noct, a partial penetration from the dentine and 



c 



FIG. 44. Sargus noct. Unerupted molar, o. Remains of enamel organ ; 

 t. open deeply stained channels in the enamel ; b. stained horizontal band ; 

 c. unstained enamel ; d. dentine. (x50.) 



a full one from the outside in Sargus vulgaris, and a complete 

 suppression of the dentinal tubes in the enamel of Sargus 

 ovis, only the tubes from without being present. It is not 

 usual to find such a marked difference of structure in the 

 enamel in species belonging to the same genus. 



In the Sparidse the teeth replace one another vertically 

 instead of laterally as in most fish. The successional teeth 

 lie immediately beneath those in use and within the substance 

 of the bone. 



If the enamel of these unerupted teeth is examined by 

 the fuchsin method it is seen to differ very considerably in 

 appearance from that of the erupted teeth (figs. 44 and 45). 



