Morphological Studies. 737 



The teeth of Myxine are very much smaller and weaker than those 

 of Bdellostoma. They are not so richly calcified, and the horn is not 

 so hard, and with a little care one can cut longitudinal sections of the 

 whole head with the teeth in situ. As before stated, they have a 

 length of about one milUmetre. 



The horny cone of each tooth has the same appearance and 

 characteristics, and arises in the same manner as that of Bdellostoma 

 (fig. 13 hg). 



Underneath it (fig. 13 s e) a stratified epithelium is met with as 

 in the latter form ; following it comes a true cellular odontoblast pulp 

 (fig. 13 c). The cell elements are like those of Bdellostoma. 



The enamel epithelium could not be found in any of the numer- 

 ous preparations , though many of the sections were by no means 

 bad. At the apex of the odontoblast cone a very small enamel cap can, 

 on careful search, be sometimes detected (figs. 5 and 13 c). It is much 

 smaller than that of Bdellostoma^ and appears to be öfter absent. Its 

 diameter is about Via 5 of a millimetre, whereas that of Bdellostoma 

 is nearly ten times as thick. 



The development of the horny teeth of Petromyzon planeri. 



After this work was already written ^) in the form in which it 

 now appears (with the exception of this section), my friend. Prof. 

 Howes, drew my attention to a paper by Dr. W. B. Scott (19) which 

 treats of the development of teeth in the Lamprey. Scott's re- 

 searches only appeared in a rather inaccessible Journal (Science), and 

 have received no mention in either of the chief „Jahresberichte" for 

 1883. Fortunately for my work Prof. Wiedersheim was able to place 

 at my disposal a number of newly metamorphosed Petromyson which 

 had been caught on Oct. 31** 1888^) in the neighbourhood of Kirn- 

 halde in the Schwarzwald. 



I will at once state what I was able to find in those specimens, 

 and then compare my results with those of Scott. 



1) April 1888. 



2) I mention the exact date as such matters are often of extreme 

 importance with reference to questions of the life-history of the ani- 

 mal. 



