Morphological Studies. 733 



tapers off rapidly towards its apex (fig. 1 oc). Below it is partially 

 hollowed out, forming a pulp cavity (fig. 1 p c) filled with blood 

 vessels, connective tissue, and (probably) nerves. 



This odontoblast cone is very hard and obviously calcified. 

 After lying in picrocarmine for weeks it is still unmacerated. 



In section it is seen to be made up of several rows of cellular 

 elements which radiate from the centre towards the circumference of 

 the tooth and slope away from above downwards. These elements 

 (fig. 4) are calcified odontoblasts. Each of them has a 

 large somewhat rounded nucleus, and the cells have a polygonal 

 tapering form. They are on the average about 0,1 millimetre in length. 

 These cells are very markedly longitudinally striated (fig. 24). 

 The striae are somewhat wavy, and appear to be the optical expres- 

 sion of structures corresponding to the dentinal tubules of ordinary 

 teeth. If Prof. Waldeyer's view i) of the mode of formation of the 

 dentine by the conversion of odontoblast substance into the former 

 structure be correct, then the correspondence would be exact, and as 

 these odontoblasts in the Myxinoid tooth are most certainly partially 

 calcified cells, the appearances they present go a long way towards 

 confirming his view. 



The pulp does not consist of a single row, but of many rows of 

 such odontoblasts. This is represented in figs. 1 and 5 and semi- 

 diagrammatically in fig. 7. 



The apex of the odontoblast cone in Bdellostoma is occupied by 

 a small bright structureless cap of something which I take to be 

 enamel (e). It has a maximum diameter of 0,075 millimetre and 

 presents more the appearance of enamel than of anything else. 



In my preliminary note on these teeth I was very much in doubt 

 whether this cap could be called dentine or enamel. My doubts were 

 removed after meeting with Waldeyer's opinion of the dentine de- 

 velopment of ordinary teeth as mentioned above. Further, the enamel 

 nature of this cap is rendered acceptable to general belief, when I add 

 that, since that time, I have been fortunate enough to discover an epi- 

 thelium corresponding to the so called enamel-organ. 



I shall here call this structure an enamel organ or enamel 

 epithelium in a strict morphological sense, since it is an epithe- 



1) See Steicker's Handbook of Histology. English Edition. Vol. I, 

 489. 



