176 



THE FRESH-WATER FISHES OF EUROPE. 



length of the longest. The dorsal fin terminates opposite to the vent. The anal 

 h'n may be truncated posteriorly to half its length. The length of tail between 

 the anal and caudal fins is as long as the head. The ventral fins reach to the 

 vent, and, like the slightly longer pectorals, are rounded. The caudal fin is 

 evenly-lobed, but not conspicuously forked. The lateral line does not descend 

 so low as in other species of Leuciscus. It is most clearly defined over the ven- 

 trals and is rarely to be traced as far as the caudal. It opens with simple pores, 

 but the last fifteen or twenty scales are not perforated with mucus canals. The 

 perforated scales are relatively higher than the scales adjacent to them ; the 

 perforation is large and occupies about two- thirds the length of the scale. 

 The scales are remarkably delicate and small; they are longer than wide, and 



Fig. 98. LEUCISCUS PHOXINUS (LINN T ;EUS). 



99. PHAKYX- 



GEAL TEETH OF 

 LEUCISCUS PHOXI- 



NUS. 



marked with a radiating fan of fifteen to twenty rays. They do not overlap 

 conspicuously, but the degree of imbrication varies with the individual and 

 locality. Scales are frequently absent from the under surface of the body as far 

 as the anal fin. The largest scales are in the tail. The 

 number along the lateral line varies from eighty to ninety. 



The Minnow varies its colour with the locality. It is 

 more brilliant when taking food ; and duller by night than 

 by day. The variability of colour is due to the existence 

 in the skin of two layers of pigment cells, which are 

 superimposed. One layer, most abundant on the back, has the cells star-shaped, 

 black, and contractile ; the other deeper-seated layer has the cells smaller, 

 somewhat rounded, of varied- colour, with the majority yellow. By the 

 expansion and contraction of the first layer the second is more or less covered 

 or exposed, and this change is accompanied by a variation in the quantity of 

 blood injected into the tissues. 



The colours are most brilliant at spawning-time, particularly in the males- 

 The back is dark brown-green, often decorated with a black line which may 

 extend to the caudal fin. The sides are greenish-yellow with a metallic 



