BY JAS. R. TOSH, M.A., B. SC. 177 



of the whiting of British waters. The latter species is one of 

 the haddock family. The species under discussion at present 

 belongs to the Trackinidae. 



Spawning Season. 



The spawning time of the whiting may be stated to last from 

 September to February. The first ripe fish taken were large 

 males in June. Ripe females occured in fair quantity in 

 September. In a female specimen just over 16 inches long and 

 weighing lib. 8f ozs. the weight of the ovaries was 3|^ ozs., or 

 about 14 per cent, of the total body weight. The fish were 

 observed to have been feeding at intervals during the process of 

 spawning. 



Development. 



The egg of the whiting is small, measuring from '68 to 

 •69 mm in diameter, and contains one oil globule, measuring 

 about -18 mm in diameter (PI. VIII. fig. 1.) It is a transparent 

 sphere, and is pelagic. On the perivitelline membrane are a 

 number of faint lines, wrinklings or thickenings of the 

 membrane. The pores in the outer capsule are visible for only 

 a very short time after extrusion. The oil globule is not 

 altogether transparent, but shows a black edging. 



After about 15 minutes in the water, the segmental disc 

 (d. fig 2), shows on the under side of the egg. Fig. 3 is a side 

 view of the disc just before segmentation begins. After fertilisa- 

 tion, cell division begins — the 2-cell stage being reached when 

 the egg has been half-an-hour in the water. Thereafter 

 the disc divides rapidly into 4, 8, 16, 32 cells — the last- 

 mentioned stage being reached at Ihr. 35mins. No horizontal 

 divisions could be seen at the 16-cell stage. Figs. 8 and 9 are the 

 large- and small-cell morula stages — the latter occuring at 2hrs. 

 40mins. Thereafter the cells become smaller rapidly, and 

 proliferating at the edge of the disc begin to envelop the yolk 

 mass. Fig. 10 at 8|hrs. shows the blastoderm almost covering 

 the yolk. (The oil globule has been omitted in figs. 3 to 10). 



When the enveloping process is all but completed, the 

 embryonic streak (em. fig. 11), is visible. At the same time, 

 9fhrs., pigment cells appear on the blastoderm especially over 

 the oil globule. They are of a light grey colour, and irregularly 

 stellate in shape. By 10 hrs. 40mins., the embryo is clearly 

 outlined — the tail being twice as broad as the head. Pigment 

 cells of a thin grey show on the body, the oil globule and on the 



