RHODEUS AMARUS. 20 ( J 



paralleled by many other Cyprinoids, like Chondrostoma. The operculum, back, 

 and sides, above the anal fin, have a beautiful violet colour. On each side of 

 the tail is an emerald-green stripe, which extends half way along the length 

 of the body to the caudal fin, and ends in a fine streak. The pectoral region 

 and abdomen are silvery, with rose-coloured or orange-red patches. Behind 

 the operculurn is a broad, vertical silver baud, covered with dark violet spots. 

 The dorsal fin is brown, spotted, almost banded, with black. The anal fin is 

 bright red, with black edges ; the pectoral and caudal fins are pale in colour and 

 transparent. The iris is very red above. 



The females are smaller, their height being about four-fifths of that of the 

 males. The head is rather longer, but all the fins are shorter than in the 

 male. At ordinary times there is but little difference between the sexes in 

 colour, but when the male puts on his metallic beauty of varied colour, the 

 female has the back greenish-brown, with the sides, abdomen, and pectoral 

 region, silvery. The line at the middle of the side of the tail varies from 

 steel-blue to black, is rarely half as wide as in the male, and often disappears. 

 All the fins are pale in colour except the dorsal, which is bordered with a 

 broad black margin. The iris is pale yellow, with orange spots. There are 

 no bony tubercles on the snout. 



There is some difference in the air-bladder, for although it is generally 

 divided in both sexes into unequal parts, the anterior third taking a pear 

 shape, this part is usually much more slender in males than in females. 



The female fish has none of the brilliant colouring of the male, but pos- 

 sesses a long orange-red oviduct, which often extends some two-thirds of the 

 length of the fish, hanging free like a worm in front of the anal fin, and 

 sometimes extending back beyond the caudal fin. It was discovered by Herr 

 Krauss, of Stuttgart. The eggs are yellow, and, when they distend the 

 external oviduct, give it a beaded aspect, as they move down in succession 

 one behind another. The diameter of the oviduct is less than that of the 

 eggs, which are elongated to a cylindrical form within it, regaining their 

 oval shape when laid. The oviduct, after performing its function, is gradually 

 shortened until it disappears in a papilla. 



The long intestine exhibits two principal convolutions, which lie below the 

 liver. Von Siebold found the entire intestine filled with diatomacese and 

 fragments of algse. The heart-shaped bladder opens into the base of the 

 oviduct, so that were it a permanent structure it might be termed the uro- 

 genital canal. 



No one has observed the mode of deposition of the eggs, or ascertained 

 whether this remarkable tube, which is furnished with its own blooJ-vessels 

 and nerves, is made use of to place the eggs in a secure position. 



