MUSEUM OF COMPARATIVE ZOOLOGY. 129 
T have frequently found in sections of scales of different ages, killed 
by various reagents, a narrow marginal zone appearing somewhat 
different from the rest of the section (Plate I. Fig.. 3, and Plate III. 
Figs. 17, 20). This often appears strikingly like a different layer 
of material, and is sharply bounded from the deeper-lying layers. I 
believe that this appearance is due to the action of reagents used in 
killing or staining (in toto), or both, and not to any natural difference 
between the parts of the scale. No such difference is found in material 
killed in alcohol. Klaatsch refrains from stating anything concern- 
ing the methods he used or the manner in which his fish had been 
killed. The impression produced by the study of his paper is that he 
was misled by some artificial condition such as I have just mentioned 
and figured. 
I have already stated that the spines frequently leave no trace of 
their existence in the adult scale. To what their disappearance is due 
I am unable to state positively. Before the outer layer begins to be 
formed they have almost completely disappeared from all the central 
part of the scale, but usually a few still remain close to the posterior 
edges. Hertwig (79, p. 7, Taf, II. Figg. 1, 2, 3, 10) has described and 
figured certain little knob-like elevations projecting up into the ganoin 
layer, and he believes them to be semnants of spines which have been 
lost. In this conclusion he agrees with that already expressed by Reiss- 
ner (59, p. 260). I have carefully looked throngh series of sections 
from two different adult “gars” for such structures, but without finding 
them. Hence it would appear that their occurrence cannot be considered 
a constant feature. In scales from one young fish 46 cm. long, however, 
I found some peculiar structures similar to those figured by Hertwig. 
One of these is shown in Plate TI. Figure 14 and is without doubt, as 
Hertwig maintained, the base of a lost spine. It had been entirely 
buried in the ganoin. There were also present a number of other 
much smaller bodies lying between the top of the scale and the over- 
lying tissue in the space from which the ganoin had been dissolved. 
These were widely scattered, and many were little larger than an odon- 
toblast cell; they were of an ovoidal or spheroidal form, and appear 
to be the same in composition as the one figured (Plate II. Fig. 14), 
and T am led to the conclusion that they are also remnants of the 
bases of lost spines, which were probably in process of absorption when 
the secretion of the ganoin began and buried them. Hence I be- 
lieve that the obliteration of spines is in general due to absorption, 
though it is hardly conceivable that the distal part of the spine dis 
VOL. XXIV —NO. 5. 2 
