76 THE FRESH-WATEi; FLSIIES OF EUrxOrE. 



The stomacli is lar^^e, and has two small pyloric appondag-es. The ver- 

 tebrae vary in uuniher from thirty-one to thirty-three. 



The colour of the back is bluish-black or g-reeuish-brown^ with the sides 

 and belly silvery. The throat and breast vary from pale rose to blood-red ; 

 the fins are transparent and g-reenish ; the pupil is oblique, and the iris like 

 silver. Tiiese colours reach their greatest intensity in the spawning- season. 

 The colours are less variable in the female and the young than in the male. 



This species is rarely more than three inches long. It is somewhat 

 tenacious of life, and will often throw itself out of the water and live in damp 

 g-rass for a time. It is very voracious, and its movements are rapid. In 

 an aquarium a small Stickleback in five hours devoured seventy-four young- 

 dace about a quarter of an inch long. They are sometimes found in such 

 quantities as to be used for manure. The fish is frequently afflicted with 

 a kind of tape-worm [Bothriocephalus solidus), which often fills the entire 

 body cavity and kills the Stickleback, when the worm is liberated, often 

 to find a resting-place and development in the duck, or some other water 

 bird. 



The Stickleback is widely distributed, and is found in shallow streams 

 in almost all parts of Europe, and in the Baltic and Frische-Haff, though 

 the varieties are dili'erently distributed. The variety a Gasterosleus 

 gymmirus, which has only four or five plates above the pectoral fin, and 

 the rest of the body naked, is found in England, France, Southern Germany, 

 and the Baltic. The variety ^ Gasterosfen.^ semiarmatus, which has ten 

 or fifteen plates on the front part of the sides, is found in England, Belgium, 

 and France. The variety 7 Gasterosteus semiloricatus, which has scaly plates 

 reaching' to the caudal region, is limited to France and Ireland. The variety 

 S Gasterosteus trac/inrits has scaly plates covering- the tail as well as the 

 body, and is found in the northern parts of Europe, England, France, and 

 Germany. The variety e Gasterosteus novehoracensis differs from (1 . trachurus 

 only in having a longer ventral spine. It is found in Greenland and in 

 North America. 



Many writers attach specific importance to these varieties, and Yarrell 

 adopted most of the types which had been recognised by Cuvier and A'alen- 

 ciennes, and are still preserved by Blanehard. 



The species appears to be wanting in the Danube. 



In Pennant^s time the Stickleback was remarkably abundant in the 

 Fens of Lincolnshire, and every seven or eight years amazing shoals appeared 

 in the Welland, at Spalding-, and came up the river in a vast column. They 

 were used to manure the land, and occasionally oil was extracted from them 

 by boiling, as in Sweden and France. As an illustration of the abundance 



