298 HYBRIDS BETWEEN THE TURBOT AND THE BRILL. 
turbot, the scales retain characters which closely resemble a very 
early condition in the development of a turbot’s tubercle, as well as 
the perfect condition of the scale of a brill. The persistence of the 
skinny covering has probably no greater significance than is explained 
by the comparative remoteness of the scales, since the imbrication 
and exposure of the free edges of the scales in the brill may be 
taken as the result of the closeness with which they are set in that 
form. 
Perhaps the intermediate character is best brought out by com- 
parison of the scales of the lateral line in the three forms. The 
body of the scale, represented in the turbot by very insignificant 
flanges, dorsal and ventral to the sensory tube, is present in the 
hybrid to a variable extent, as may be judged from comparison of 
band c (Fig. 3). In no case is it so well developed as in the 
brill (a), nor so insignificant as in the turbot (d). 
Fid. 3.—a. Scale from lateral line of brill (blind side). 6, c. From hybrid (blind side) 
d, From turbot (blind side). 
Conclusions.—In discussing the parentage of these forms it 
appears to me that there are only two alternative theories, since it 
is not likely to be seriously contended that they belong to a distinct 
species. They may be either hybrids, or ‘sports ”’ of either the 
turbot or the brill. If the latter is the true explanation it 1s at least 
remarkable that the variation should in so many points tend towards 
the typical characters of another species, and I cannot but think 
that the sexual immaturity of all three specimens (considering their 
large size) is strong evidence of hybridity. As to whether the female 
