THE SCALES IN SOME TELEOSTEAN FISH. 49 
took portions of the skin of the same animal and from the 
same region of the body, and treated it with borax carmine 
and acid-alcohol. The sections obtained showed precisely 
the characters figured by Klaatsch. ‘The scales are seen on 
section to form an elongated continuous plate from which 
project several small pointed elevations at the caudal and 
cephalic ends. Owing to having been decalcified, the organic 
basis of the placoid scale has become stained, like the sub- 
stratum below and between them, and thus gives the appear- 
ance of continuity. Though Klaatsch figures these tooth-like 
elevations, he does not appear to have recognised their 
morphological value. Indeed, in his lengthy memoir I have 
not noticed any particular reference to them, beyond the 
general statement (p. 196): “Der Spitzentheil der 
Placoidschuppe ist mit wenigen ausnahmen vollig 
reducirt. Die Oberflache der Teleostierschuppen 
geht neue Komplikationen ein, welche zu mahnig- 
fachen Reliefbildungen fihren.” 
The scale continues to increase at its periphery by the 
addition of more denticles, so that meeting and overlapping 
the adjoining scales they become imbricated. Asa result of 
this growth, that part of the dermis superficial to the scale 
cavity becomes stretched and thinned. Accompanying this 
increase in size of the scale, there is a progressive conversion 
of the subjacent nucleated layer into fibrous tissue, which 
thus in course of time presents a laminated appearance, cer- 
tainly as many as five layers coming to be ultimately formed. 
I would draw attention in passing to the fact that this con- 
version into fibrous tissue is from above downwards—that is, 
it follows the direction of growth which Huxley maintained 
to be the character of enderonic tissues. ‘The bearing of 
this point will be discussed subsequently. 
As a result then, of the continuous growth of the scales in 
a closed cavity, there is stretching of the less rigid tissues of 
the roof, and at the same time the “pull” exerted by it 
would tend to crowd the denticles together, and also to keep 
the growing margins of the scale upturned. ‘This mechanical 
vou. 49, parry 1,—NEW SERIES. 4 
