170 TIIK FHESTI-WATEi; FTSTIES oF FFlJoPF. 



leiii:^th of the lonor-est. Tlio dorsal fin terminates opposite to the vent. The anal 

 fin may be truncated posteriorly to half its leng-th. 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 

 ])erforated scales are relatively higher than the scales adjacent to them ; the 

 ])erforation 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. LEUCISCIS PHOSINVS (LINN'-^Ers). 



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



consi)icuously, but the degree of imbrication varies with the individual and 



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



R ^pyv as the anal fin. The largest scales are in the tail. The 



^^ A^. number along the lateral line varies from eighty to ninety, 



wi-^pU,G3fcj The Minnow varies its colour with the locality. It is 



GEAL TEKTH OF uiorc brilHaut when taking food; and duller by night than 



LEiciscvs i-Hoxi- -^^ ^^y rpjjg variability of colour is due to the existence 



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



superim])oscd. 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 lin. The sides are greenish-yellow with a metallic 



