56 H. W. MARETT TIMS. 
there have been lines of intermission which become more 
visible on staining. This is due to the deficiency of the cal- 
cified upper portion of the scale allowing the underlying 
fibrous (staining) stratum to be visible. 
Though these lines of intermission occur with a certain 
amount of regularity, I do not think they can be regarded 
as delimiting the different periods of seasonal growth of the 
scale, fortworeasons. In the first place, they are not always 
of equal number in scales removed from the same situation 
in the same fish; and secondly, they do not always extend 
around the anterior moiety of the scale, but are often 
interrupted so that the excentric (calcified) lines of one area 
pass into those of the area next toit. I believe these lines of 
intermission have little, if any, morphological value. 
All markings are absent from the posterior uncovered 
portion of the scale, the calcified layer being smooth and of 
extreme thinness. 
Examination of a section through the scale shows that the 
excentric lines in the anterior part are due to minute ridges 
arising from a continuous basal calcified layer, each ridge 
having an inclination towards the centre of the scale. 
The fibrous portion of the scale has an arrangement 
similar to that previously described for the cycloid scale, but 
in one section the perpendicular tubules are slightly larger. 
Sections through the long axis of the scale in a young 
herring show the same placoid condition as in the young 
cod, the individual scalelets being much more minute. The pro- 
jecting spines in the median line of the scales are backwardly 
directed, as in the Elasmobranchs ; that is, they have the same 
inclination as that of the excentric markings in the adult 
scale. These placoid scales are limited to the anterior 
portion of the scale, the scalelets of the posterior portion being 
merely elongated flattened plates without any spines. 
T cannot say whether they have been present and have 
disappeared, but I have never seen them, though I have 
examined fish of various ages, and I am inclined to think 
that that portion of their philogenetic history has disappeared 
altogether from their ontogeny. 
