BULLETIN OF THE 
and in connection 
in the scleroblastic dermal cells to become osteoblasts, 
it has developed a system of tubules for supplying 
Moreover, instead of being formed simply as a 
it has come 
with this process 
them with nourishment. 
continuation of the process by which the spine is produced, 
pine, for it is only in a late stage of its 
to develop independently of the s 
Thus the Ganoid scale plate seems 
growth that the two become united. 
to have arisen from the placoid basal plate by increase in size and with 
important modifications. 
2. The spine, on the other hand, has become reduced in size and in 
Ganoids (Lepidostens) only a rudi- 
complexity of structure, and is in 
early, as is frequently the 
mentary organ arising late and disappearing 
case with degenerate. structures, the “ wisdom teeth” of man being a 
familiar illustration of this. 
Hertwig’s view is that the scales of Lepidosteus have arisen by the 
fusion of numerous smaller basal plates of scales of the Selachian (pla- 
coid) type. Each spine upon a scale of Lepidosteus therefore represents 
a primitive placoid scale, and the whole Ganoid basal plate has arisen by 
the fusion of as many simple scales as the total number of spines formed 
Klaatsch objects to this interpretation, since the 
upon its surface. 
and because the 
number of spines is so large and wholly indefinite, 
spines lack such an orderly arrangement as that which the scales have 
in selachians. 
My own view in regard to t 
expressed by the latter author. 
regarded as a more highly developed basal plate 
is not due to the fusion of many small ones, but 
l in connection 
his matter is essentially the same as that 
Though the Ganoid scale must be 
than that found in the 
Selachians, its origin 
rather to the calcification which in Selachians originate 
with the formation of placoid spines, having become in 
yon the impulse given by 
Lepidosteus 
an independent process no longer dependent uy 
the growth of the spine. The hereditary tendency toward the growth 
pille still shows itself, however, in the formation 
and calcification of ] 
hose aro retarded in time and but feebly 
of the small spines, though t 
developed. 
As long as each spine had a basal plate, as in Selachians, the spatial 
requirement of this plate exercised a, controlling influence upon the num- 
spines). When now, as in 
ber and the arrangement of the scales (= 
independently of the under- 
Lepidosteus, the spines have come to arise 
lying plate, such restraint is removed, and we consequently find an in- 
crease in the number of the spines and a lack of regularity in their 
arrangement . 
