DEVELOPMENT OF THE TEETH OF FISHES. 
265 
The enamel-organ, which attains but a feeble development, was seen by Prof. ITuxley 
to be continuous with the oral epithelium ; to his description I have only to add that 
the first step towards the formation of a new tooth-germ is the budding inwards of the 
oral epithelium (which has been lost from the surface of the section figured). 
The tooth-germs of the pike originate in precisely the same manner as those above 
described ; but it is not unusual to see two tooth-germs of different age apparently 
destined to succeed to the same tooth, a thing which I have not observed in the 
haddock, the eel, or the perch. 
The enamel-organ of the pike attains to a development intermediate between that of 
the mackerel and that of the eel or perch ; from the regular appearance and consider- 
able size of its component cells, which measure from xoVo to ^oo °f an inch, I should 
anticipate that a layer of enamel would be found upon its teeth, which is apparently 
the case, though it is not very thick. 
Although the enamel-organs of all these fish consist primarily of two rows of cells, and 
traces of their original formation may be in places discerned, as at the base of the enamel- 
organ in fig. 11, yet that layer of columnar cells which goes by the name of the “enamel 
epithelium ” so greatly preponderates that the outer layer is soon lost sight of. 
No stellate reticulum separates these two layers in any fish or reptile with which I 
am acquainted. 
There are many points of importance which I have not touched upon in this short 
and imperfect paper — such, for example, as the presence or absence of a basement 
membrane or membrana preformativa upon the dentine-papillae, as well as the sub- 
sequent details of the process of calcification. My object has, however, been merely to 
give a general outline of the subject, which I hope at some future time to fill in with 
greater detail. 
My examination of the process of the development of the teeth having been now 
extended to a considerable number of Mammals, ftep tiles, Batrachians, and Fish, justifies 
me in drawing some general conclusions as to the structure of the tooth-germs, the 
more important of which may be summarized as follows : — 
1. It is desirable to entirely abandon the terms “papillary,” “follicular,” and 
“ eruptive ” stage, inasmuch as these are hypothetical and arbitrary, and correspond 
to no serial conditions verified by observation. 
2. In all animals the tooth-germ consists primarily of two structures, and two only — 
the dentine-germ and the enamel-germ. 
The simplest tooth-germ never comprises any thing more. When a capsule is 
developed it is derived partly from a secondary upgrowth of the tissue at the base of 
the dentine-germ, partly from an accidental condensation of the surrounding connective 
tissue. 
3. The existence of an enamel-organ is quite universal, and is in no way dependent 
•upon the presence or absence of enamel upon the completed tooth, although the degree 
to which it is developed has distinct relation to the thickness of the future enamel. 
mdccclxxvi. 2 p 
