THE SCALES IN SOME TELEOSTEAN FISH. 59 
scale in which the spines might persist only in the anterior 
covered field, as in many scales of the ctenoid type; a 
further suppression of the same would lead to the cycloid 
pattern. The tendency to lateral fusion of the scalelets so 
frequently seen in the latter would give rise to the scales of 
the clupeoids, the degree of fusion being seemingly correlated 
with the relative increase in size of the scale. A still further 
stage of suppression is seen in the herring, where not only all 
vestiges of the spines are wanting, but the scalelets themselves 
have almost disappeared from the uncovered posterior field. 
The phylogenetic order of the scales would, therefore, 
appear to be placoid, ctenoid (?), cycloid, and lastly, clupeoid, 
and as far as the Gadide are concerned ontogeny recapi- 
tulates the phylogeny. I hope shortly to have completed 
researches into the development of the ctenoid type. 
Within the limits of the Gadidz one meets with unmis- 
takable signs of fusion of the scalelets in G. minutus and 
G. wglefinus, which, in the earlier stages, are quite dis- 
tinct. A further advance in the same direction gives the 
clupeoid scale. One reason for regarding the cycloid scale 
as a ctenoid in which the spines have almost (G. callarias) 
or entirely (G. virens) disappeared has already been given. 
There are, however, certain other facts which tend in the 
same direction—for example, the fact that the scales on 
the blind side of Arnoglossus are cycloid, while on the 
ocular side they are ctenoid. Further, the opercular 
bones in the turbot and many other Pleuronectids are 
heavily armed in the young, whereas they are smooth in 
the adult. Again, the ctenoid scales in the dwarf variety 
of the plaice (Pl. pseudoflesus) may be taken as another 
indication in the same direction. 
On the other hand, Dunker (4) states that in the male 
plaice after maturity the cycloid may develop into ctenoid 
scales, and that the same may happen in flounders only 
2-3 cm. in length. I do not wish to pass lightly over any 
point adverse to the views here expressed, but I may be per- 
mitted to refer to the opinion of an independent reviewer, 
