i8o 



MARKETABLE BRITISH MARINE FISHES 



separation of the membrane was 1-5 to r6 mm. (^^^j^ inch), but 

 after the swelHng of the membrane its breadth was 4-2 to 4-6 

 mm. (yW inch). 



The newly-hatched larva is just over ^VV inch long. It is 

 extremely transparent, and has no mouth and very little pig- 

 ment, so that it resembles that of the sprat. Ehrenbaum was 

 able to trace its transformation to the fully developed form, and 

 its history, with considerable completeness. 



Fig. 93. — Larva of the Tvvait Shad, nearly f incli long ; after Ehrenbaimi. 



The eggs naturally deposited were obtained from the bottom 

 at the end of May by sinking a fine-meshed tow-net. They 

 were quite free, but being so transparent were not easy to find 

 among the rubbish, consisting of fragments of plants, among 

 which they were taken. The larvae in various stages were 

 captured in the same manner. When 8 to 9 mm. (t/V to J^ inch) 

 long the yolk was nearly all gone, the mouth well developed, 

 and the fin membrane narrow. But the permanent fin ra}'s had 

 not appeared. In June larva; were obtained which were 13 to 



s^ 



Fig. 94. — Larva of the Twait Shad, i inch long ; after Ehrenbaum. 



15 mm. long" (Fig. 93), and in these the dorsal and ventral fin 

 rays had just begun to appear, but the fish was still slender and 

 transparent and the snout rounded. At the end of June speci- 

 mens 16 to 20 mm. long were taken : in these the forked tail 

 and the fins were more fully developed, and the head was more 

 like that of the adult, but the scales were still absent (Fig. 94). 

 These larvae were feeding on minute Crustacea. 



On July 6th specimens were obtained which were 24 to 29 



