414 THE HERRING FAMILY. 



the yolk-sac but runs ventrally to the notochord for a long 

 way, the vent being situated at a point about l of the total 

 length of the larva from the tail-end. This character appears 

 to be common to all the clupeoids yet observed. Other clu- 

 peoid features are the unicolumnar notochord, the ovoid 

 condition of the yolk-sac and the vesicular yolk. No ventral 

 fins are yet present. The median embryonic fin is of course 

 continuous and extends for a short distance upon the posterior 

 border of the yolk-sac. In some instances pigment is found in 

 the newly hatched herring and appears after a day or so in 

 others. Black pigment is alone present, and ' consists of one 

 or two median chromatophores below the heart, a chain 

 of about ten commencing behind each pectoral fin and 

 running backwards on each side of the gut for about half its 

 length ; an irregular, sometimes double, chain ventral to the 

 posterior half of the gut ; two (sometimes one) stellate chroma- 

 tophores on each side, a little in front of and above the vent. 

 Stellate chromatophores are also developed above the posterior 

 end of the notochord, and more abundantly below it' (Holt). 



Growth and development are rapid, and the yolk-sac is 

 usually absorbed in about three or four days. Whilst this is 

 being accomplished, the larva gains considerably in strength 

 and activity, though still keeping near the bottom (Plate XIX, 

 fig. 3). They are to be caught in great numbers in the bottom 

 tow-net. The demersal habit therefore extends to the very 

 early larval stage as well as to the embryonic. It will be 

 remembered that the larval sprat and pilchard float helplessly 

 in the surface- or mid- water, and are thus pelagic, as are the 

 eggs of these two species. 



The post-larval herring, however, freed from the encum- 

 bering yolk-sac, and probably led by its search for food, leaves 

 the bottom and migrates into the mid-water. As a rule, these 

 active little post-larval herrings may be caught in St Andrews 

 Bay at the end of March, in the mid-water tow-nets, at about 

 4 fathoms. 



The length of 10mm. is reached at this stage. The 

 eyes are prominent, with the same bluish sheen and black 

 border which have been already noticed, the mandible projects 



