74 



angles, but arranged quiucuncially, the rectangular lines cannot easily be followed, 

 but two oblique or diagonal series become conspicuous. It is the oblique rows of 

 scales, either those from right to left or from left to right, which are counted in 

 describing the specific characters of a fish. 



The imbedded portion of a scale exhibits a number of parallel curved lines, the 

 edges of the lamiuLE of which it is composed. The directions of these lines divide this 

 portion of the scale into three areas : a triangular area bounded by the anterior edge 

 of the scale and two lines which meet at an acute angle near the anterior apex of the 

 spinous portion, and two similar areas on either side of this. The anterior portion is 

 divided up by a number of radiating straight lines, into radiating strips, eaah of which 

 is occupied by a series of short curved parallel lines. The two other areas are 

 occupied by lines parallel to the dorsal and ventral edges of the scale. 



The scales of Solea lascaris, variegata, and lutea resemble those of S. vulgaris in 

 structure. The scale of lascaris, Fig. 4, PI. XIV, is the lai-gest : it has the same 

 general shape as that of vulgaris, but the spines are more pointed, and there are 

 seventeen rows of them, and six spines in each of the central rows. The scale of 

 variegata, Fig. 3, is shorter in proportion to its breadth than that of lascaris, it has 26 

 rows of spines, with eight spines in each central row : the spines, except the most 

 external, are short and blunt. The scale of lutea. Fig. 5, is the smallest of the four : 

 in shape it resembles that of vulgaris ; it has 21 rows of spines, four spines in each of 

 the central rows ; the spines are rather short and pointed. 



The " lateral line " which runs down the centre of each side of the sole is formed by 

 a series of scales which are very different from the ordinary scales of the body. They 

 have no spines, and no portion of them projects beyond the surface of the skin. One 

 of these scales from Solea vulgaris is represented in Fig. 2, PI. XIV. Anteriorly its 

 structure resembles one of the ordinary scales, but posteriorly it is narrowed to a blunt 

 apex and the spinous portion is wanting. On its external surface, for a little more 

 than half its length posteriorly, there runs a kind of tunnel with rounded roof which, 

 with the scale below, forms a tube open at both ends : this tube or tunnel is broader in 

 front than behind. In the floor of the tunnel, not far from the posterior end of the 

 scale, is a large oval aperture. These scales of the lateral line overlap one another in 

 such a way that the aperture in the floor of the tunnel of one is just in front of the 

 anterior aperture of the tunnel of the scale behind it. 



Dermal Canals and Sense-organs. 



This system consists of a number of connected tubular channels running in the 

 derma or in bones originally derived from the derma. The longest and most easily 

 observed of these tubes runs beneath the lateral line. It is lined by a cellular layer 

 somewhat similar to the superficial epidermis, and it runs through the series of bony 

 tubes just descriljed as belonging to the scales of the lateral line. Tracing the tube 



