186 MICROSCOPIC ANATOMY OF THE TEETH 



being in the immediate neighbourhood of the forming 

 enamel. Similar conditions exist in the Labridse, as will be 

 presently explained. If, however, in the Gadidse the presence 

 of cells in the enamel organ is substantiated, this anomaly 

 would cease to exist in them also, although the absence of 

 blood-vessels in this family would not bring about quite 

 the same conditions, and the deposit of the lime salts would 

 be probably due to a process of dialysis as in mammalian 

 tooth germs. 



It was shown that in Sargus ovis the portion of enamel 

 next to the dentine is not traversed by any enamel tubes 

 but consists of interlaced enamel prisms. In Sargus noct 

 and 8. vulgaris it is traversed by tubes (figs. 43 and 44), 

 but these are derived from the dentine. Tomes also points 

 out that the inner layer of enamel in the Gadidse is not 

 tubular. It would appear that this is the portion of the 

 enamel laid down by the ameloblasts, the tubular portion 

 of the enamel both in Gadus and Sargus being deposited 

 by the structure which arises after the disappearance of the 

 ameloblasts. Further investigation is desirable to ascertain 

 if this secreting structure is confined to those enamels 

 which are traversed by tubes from without, as we know 

 that in many osseous fish the whole enamel appears to be 

 deposited by ameloblasts as in Mammalia. 



As pointed out in a former chapter, a thin pellicle of the 

 enamel organ remains attached to the surface of the enamel 

 when it is apparently completed and just about to erupt. 

 It appears as if, at this late stage, when the calcification has 

 reached the inner surface of the capsule, the enamel is in 

 direct contact with the blood-vessels at the margin, for nuclei 

 of blood-vessels can be sometimes detected in the tubes, 

 which at this stage are widely open and very incompletely 

 calcified (fig. 46). 



In studying the development of the tubular enamel of 

 the Labridse or Wrasses, the following examples were taken : 

 Tautoga onitis, the Black fish of the Atlantic coast of 

 America ; and two Japanese fish, Halichoeres pooecilopterus 

 and Pseudolabrus Japonicus. 



The enamel organs of these fish also show a similar 

 secreting structure to that of Sargus, but there are some 



