MUSEUM OF COMPARATIVE ZOOLOGY. 128 
Almost as soon as the calcareous material of the scale begins to be 
laid down some of the surrounding scleroblasts become enclosed by it 
(Fig. 3). This process goes on hand in hand with the increase in the 
size of the scale, and as a result the scleroblasts are distributed through 
all parts of it. That the distribution is a fairly regular one may be 
seen from Figure 15 (Plate IL) aud Figure 21 (Plate IIL). In a scale 
from which the soft parts have been removed by treatment with caustic 
potash, the cavities occupied by these cells may be very distinctly seen. 
Each one has leading from it a small number of canals (canaliculi) 
which branch and traverse the scale to unite with similar canaliculi 
from the neighboring cavities. Thus the whole scale is traversed by a 
network of fine ramifying tubules connecting the osteoblastic cavities, 
As may be seen in section, however, all the canaliculi from a given 
cavity show a tendency to spread out in a plane parallel to that surface 
of the scale within which it has been buried, so that the cavities in most 
intimate connection are those which lie at the same distance below the 
surface. Thus the material of the scale is divided into more or less 
regular lamellie of calcareous matter alternating with successive layers 
of cell cavities and their connecting canaliculi. These cavities are in 
communication with the exterior by means of canals which penetrate 
the scale and break up at their inner ends into fine tubules to join the 
canaliculi. They penetrate from both the upper and the lower surface, 
though much more abundantly from the lower (Plate II. Fig. 15, and 
Plate III. Fig. 21). At the opening of each of these canals at the 
surface of the scale there is a large cell (Plate I. Figs. 8 and 9, Plate III. 
Fig. 22, Plate IV. Fig. 23), from which a process extends into the lumen, 
These cells were called by Hertwig “Odontoblasten,” and the canals oc- 
eupied by their processes * Dentinróhrchen." I must, however, agree with 
Klaatsch that the names are poorly chosen, for the reasons set forth by 
him. The constant character of dentine, as the term has been used, 
is the absence of enclosed cells, and as the substance penetrated by 
the processes of these cells contains such elements (osteoblasts), it seems 
undesirable to call it dentine or the cells odontoblasts. Hertwig's nomen- 
clature rests on an assumption of homology which has not been proved 
true. However, as these terms have been adopted in the literature, it is 
perhaps inadvisable to introduce new ones at this time. Besides the 
odontoblasts with their processes extending into the dentinal tubules 
which Hertwig describes and figures (79, p. 5, Taf. III. Fig. 4), he 
mentions the presence of a granular substance partially filling the lumen 
of the canals. Klaatsch asserts that cells are present in the dentinal 
