DEVELOPMENT OE THE TEETH OF FISHES. 
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d. Dentine-papilla. 
e. Enamel-organ. 
e x . Rudimentary portion of enamel-organ. 
f (fig. 1). Point of passage of the oral epithelium across on to the thecal fold. 
g. Cap of enamel. 
h. Bone of jaw (or cartilage in figs. 1, 2, 3). 
1. Formed dentine, or completed tooth. 
sjo. Permal spines. 
(The lettering applies to all the figures.) 
Eig. 2. More highly magnified portion of the same section, showing the structure of 
the enamel-organs, the relation of the dentine-papillae to the mucous 
membrane, and the manner of fixation of the teeth. 
Fig. 3. Section of the lower jaw of a dogfish about 3 inches long. The continuity of 
the skin carrying dermal spines with the mucous membrane and its teeth is 
well seen. 
Fig. 4. General view of the relations of the oral epithelium to the young tooth-sacs; 
three teeth in place, which have lost their enamel tips, are shown, while on 
the right the lip is seen in outline. From the lower jaw of a perch, X 30. 
Fig. 5. Tooth-sac of a perch, showing the continuity of the oral epithelium with the 
enamel-organ, the large enamel-cells at the upper part of the latter, and its 
rudimentary lower portion, &c., X 70. 
Fig. 6. Transverse section of the lower jaw of a sharp-nosed eel; for the sake of clear- 
ness the subepithelial connective tissue has been left out. 
Fig. 7. Very young tooth-sac of an eel, X 100. 
Fig. 8. Tooth-sac a little more advanced, in which more dentine and enamel have been 
formed : the aborting of the enamel-cells at the lower edge of the enamel- 
organ is noticeable, X 70. 
Fig. 9. Tooth-sac yet more advanced, in which the terminal cap of enamel is complete} 
and the enamel-organ has almost disappeared at the upper end of the sac, 
X 30. 
Fig. 10. Single tooth of a sharp-nosed eel, showing its enamel cap and its supporting 
hollow column of bone, X 20. 
Fig. 11. Young tooth-sac of a pike, X 70. 
Fig. 12. Section of the lower jaw of a mackerel. The young tooth-sac is seen to be 
lodged in a groove in the edge of the bone : the oral epithelium is lost over 
the surface of this groove, but the neck of the enamel-organ is distinguish- 
able, X 40. 
Fig. 13. Tooth of a mackerel, showing the peculiarity of the attachment of the per- 
fected tooth, which is fixed in place by numerous slight trabeculae of new bone, 
which unite it to the margins of the groove in the edges of the jaws, X 15. 
