THE HERRING FAMILY 179 



Breeding. The time of their ascent up the rivers is men- 

 tioned in Day's British Fishes, namely, from about the middle 

 of April in the Severn for the twait shad, May to the middle of 

 June for the allis. 



But no scientific study of the eggs or the development or 

 history of the young has been made in Britain or Ireland. For 

 accurate information we are indebted to observations made in 

 France and Germany. At Elboeuf, on the Seine, twelve miles 

 above Rouen, there is a hatchery for the artificial propagation of 

 these fish, arid it was there that Professor Pouchet studied the 

 eggs in 1889. The eggs of the two species are very similar to 

 one another. They are heavier than the fresh water in which 

 they develop, and therefore sink, but unlike herrings' egg they 

 are not adhesive. They remain free and separate at the bottom 

 of the river, carried down by the stream, or back again by the 

 tide. They are spawned in May and June. 



With regard to the structure of the egg it resembles that of 

 the pilchard without the oil globule. The yolk is subdivided, 

 and there is a large space between it and the egg membrane. 

 The latter in the twait shad measures about 4-5 mm. or 

 nearly -^ inch, while the yolk is only 175 mm. or y^ inch. 

 The eggs at a temperature of 66 hatched on the fourth day 

 after fertilisation. 



The eggs of the American shad (Clitpea sapidissima] are 

 hatched annually in millions by the United States Fish Com- 

 mission, and the fish now seems to be almost as completely a 

 product of cultivation as the oyster is with us. The eggs are 

 shed in fresh water, in which they sink, but remain free and 

 separate. The egg membrane is about T V^ inch in diameter, 

 the contained egg being about half as wide. The yolk is 

 divided and without oil globule, so that the resemblance 

 to the egg of the European shads is very close. 



Recently a careful study of the twait shad in the Elbe has 

 been made by.Ehrenbaum,a German naturalist. He found that 

 this species spawned near the mouth of the river, just above the 

 brackish water, below Hamburg, while the allis shad ascends in 

 the Rhine to spawn as far as Basle, and in the Elbe above 

 Dresden. The spawning took place only at night, and the fish 

 rush about during the process so as to make a swishing noise in 

 the water. The egg of the twait shad when first shed before the 



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