IN THE SOUTH- WESTERN DISTRICT. 117 



of the egg. The unidentified form doubtfully assigned by Raffaele to 

 Coryphaina furnishes probably another instance of a completely 

 segmented yolk in the Acanthopterygian group. 



I have failed to secure any further scad in spawning condition, but 

 have no hesitation in assigning to this species certain tow-net ova 

 obtained first at Marseilles in 1895 and again at Plymouth in 1897. 

 I have described and figured these eggs, with the larviL^ hatched from 

 them, and some later stages, in the Annales du Musde dc Marseille, 

 and must refer to that publication for the illustration of my present 

 remarks. 



It will be remembered that the ripe ovarian eggs obtained at Grimsby 

 exhibited an oil -globule, indifferently cupreous, yellow or colourless, 

 and usually divided into several small globules at the time of spawning. 

 The Plymouth eggs are smaller than the Grimsby specimens, but 

 larger than those met with at Marseilles. 



Diameter of egg. Diameter of oil-globule. 



*Grimsby . . 1-03-1 -09 mm. ... •2G--27 mm. 



Plymouth . . -81- -93 „ ... •22--23 „ 



Marseilles . . -76- -78 „ ... •19--20 „ 



I believe that this difference corresponds to the size of the parent 

 fish in the several localities. As between the North Sea and the 

 south-west coast I am not sure that the difference is considerable, 

 but as spawning seems to be at its height in the North Sea in May, 

 and my Plymouth ova were not taken before July, I suppose that 

 the latter were derived from the smallest parents, which seem to spawn 

 as a rule later than the large ones. As to the Mediterranean scad, all 

 that I saw at Marseilles were very much smaller than the large 

 Atlantic variety or race, and I. imagine that in comparative size the 

 scad differs, in the two seas, as the mackerel and pilchard are well 

 known to differ. 



Apart from the difference of dimensions the Plymouth and Marseilles 

 ova are identical, and agree in character with the ovarian egg of the 

 scad. The yolk appears to me to be absorbed rather more quickly 

 than in the majority of pelagic eggs, having regard to the degree of 

 development of the embryo, a circumstance which seems to be possibly 

 explained by the greater extent of the protoplasmic element, limited 

 in most ova to the periblast, but here extending inwards as the walls 



• An uuiJcntifictl egg, 1'29 mm. in diameter with an oil-globule of 'lO mm., is described 

 and ligured by M'lutosb (loc. cit.) from the east coast of Scotland. It may jiossibly be 

 that of C. trachurus, but the nature of the markings shown on the yolk, which rather 

 resemble yolk segments, was not ascertained. As the author observes, they may be 

 simply superficial. 



