164 THE MACKEREL FAMILY. 



(Holt). The mouth has appeared and is open. The eyes 

 are intensely black. There is a tendency, in other parts, 

 to lose the black pigment. The oil-globule has now only 

 yellow pigment, and the black pigment on head and trunk 

 is sparse and confined to the median dorsal and ventral regions. 

 A black mass, however, appears on the dorsal wall of the 

 abdominal cavity. The yolk is rapidly disappearing. At the 

 ninth day the larva (Plate VII, fig. 2) has increased to 4'88mm. 

 in length. The yolk has disappeared and the oil-globule is 

 reduced to very small dimensions. The lower jaw projects and 

 the eyes are, by reflected light, a brilliant blue. The black 

 pigment has increased in the dorsal region of the abdomen but 

 decreased elsewhere. At the 10th or 11th day the post-larval 

 condition is reached, and of the stages beyond this we know 

 nothing. 



Holt points out the strong resemblances of the larval 

 mackerel to the larval dittiis. He emphasises in his comparison 

 the following characters in common : — the absence of pigment 

 on the marginal fins, yolk-sac, and general surface of the yolk ; 

 large stellate black spots on the head and anterior region 

 generally ; a mass of black pigment on the roof of the abdominal 

 cavity, and the tendency of the black pigment on the trunk to 

 be arranged longitudinally (not in transverse bars, as in the 

 gadoids generally). If this could be construed into any racial 

 connection between the mackerel and the cottoids, then the 

 latter might be regarded as relations of the former who have 

 not become adapted to a pelagic life but have remained littoral 

 in habit, but this is mere conjecture. 



There seems good reason for holding that the embryos in 

 the egg and the larvas drift landwai'ds in the way described for 

 the cod and haddock and that the post-larval (Plate VII, fig. 2) 

 and young stages are passed in the inshore waters. Dunn 

 states that at Mevagissey the young fishes, about 3 inches long, 

 occur in the bays during August and September, leaving for 

 the deep sea in November when they are from 6 to 7 inches 

 long, and by the time of their reappearance the following June 

 they reach a length of 8 or 9 inches. 



Prof. Sars believed that at the end of the firfst vear the 



