122 BULLETIN OF THE 
becomes modified over the scale papillee to form an enamel membrane, 
though this never becomes functional and the cells soon lose their 
specialized character. Klaatsch studied the same form, and very 
positively denies that any such modification takes place. He says 
(p. 159): “Speciell die basale Epithelschicht lässt auch nicht die 
geringste Veränderung wahrnehmen.” In view of this conflict of 
testimony, it seems more probable that the differences in the condition 
of the basal cells of the epidermis observed by Hofer were due to vari- 
ations in different individuals than to changes normally taking place 
in the same individual. 
At a little later period these areas of dermal thickening have 
extended laterally until their edges have become confluent, and the 
dermis may then be described as made up of two layers, an outer 
spongy layer and an inner fibrous layer, though no definite line of 
demarcation separates the two. ‘This is the earliest stage described by 
Klaatsch, At the time when the formation of the scale begins, the 
spongy layer in its thickest parts is about equal in thickness to the 
deeper fibrous layer. The places in which scale formation is to take 
place are indicated by a somewhat greater thickness of the spongy 
layer. 
The scale first appears (Fig. 3) as a thin sheet of calcarcous secreted 
matter in the midst of the outer layer of the dermis. It is surrounded 
on all sides by the dermal cells, which lie thickly accumulated around it 
and cover it on its outer surface from two to four cells deep, completely 
separating it from the epidermis. Around its margin the cells lie closely 
packed, and at the posterior edge are particularly numerous. To these 
dermal secreting cells Klaatsch has given the name “ Scleroblasten,” a 
term which I shall adopt in referring to them. 
The scale plate is not quite parallel with the surface of the body ; its 
posterior margin is very slightly inclined outward, and with the sclero- 
blasts around it forms a low elevation against the base of the epidermis 
(Fig. 3). 
Secreted matter is not deposited where blood-vessels from below pierce 
the outer or scleroblastic dermal layer, and consequently openings through 
the scale result at such places. These persist to form the canals which 
pierce the middle area of the adult scale (Haversian canals of authors). 
The vessels which traverse them ramify upon the outer surface of the 
scale to supply nourishment to the overlying scleroblasts. No difference 
in character could be detected between the cells on the upper and those 
on the under side of the scale. 
