Morphological Studies. 735 



epithelium is no longer complete, but is ruptured at its apex, and 

 only extends partly along the odontoblast cone. 



This enamel epithelium in Bdellostoma has all the charac- 

 teristics usually ascribed to such an epithelium. Fig, 6 and 8 {e e) are 

 intended to illustrate these peculiarities. The figures are taken from 

 near the apex of the enamel epithelium in a tooth like that figured 

 in fig. 7. Fig. 6 is a drawing of a portion of this epithelium under 

 high magnification. 



It shows a high columnar epithelium (e e) resting on the odon- 

 toblast cone (o c). The cells form that beautiful palhsade epithelium 

 so characteristic of the so called enamel organ. Any one acquainted 

 with the appearance of that epithelium in the developing tooth of a 

 shark or lizard will find no difficulty in admitting the resemblance. 

 The bases of the cells rest on the odontoblast cone, and it is worthy of 

 notice Hhat a few small cells lie at the basis of the enamel epithelium 

 (fig. 6 s c). 



Each cell is longitudinally striated. It is long and narrow, about 

 0,02 milUmetre in height, and the nucleus lies not far from the outer 

 end. 



This enamel epithelium extends down along the cone to the 

 borders of the pulp cavity, nay, it even seems to be continued for 

 some distance up the pulp cavity, but closely embracing the odonto- 

 blast cone. Ultimately, however, it is reflected from the tooth, and 

 passes over into the outer epithelium. 



In the other direction , that is, towards the apex of the tooth, it 

 slopes 0Ô gradually, and almost flattens out on the cone (fig. 7). 

 It ends somewhat suddenly about half-way along the cone. 



The outer epithelium (oe) which begins at the inner side 

 of the horn groove, and passes downwards along the cone to the 

 border of the pulp cavity, ends in the enamel epithelium as described 

 above. 



It has the characters of the deeper layer of the ordinary epi- 

 dermis, and, like the latter, gives rise to a stratified epithelium (se) 

 which grows up between the odontoblast cone and the horny cap, 

 and probably helps to thicken the latter, at least in young ani- 

 mals. 



It appears to me that a portion of this stratified epithelium also 

 arises from the enamel epithelium (fig. 8). At least so I explain 

 the split in fig. 8 in the middle of the stratified epithelium. 



