St. Andrews Marine Laboratory. 45 



of Dr. Fulton and the practical skill of Mr. Harald Dannevig 

 at the Dunbar hatchery of the Fishery Board have at length 

 made it possible to give a more complete account of the deve- 

 lopment of this important fish. It is remarkable that few, if 

 any, eggs of the turbot are found in our insliore waters 

 either at the surface, in mid-water, or at the bottom ; indeed, 

 it is one of the ova that has hitherto escaped capture in the 

 tow-nets of the laboratory, closely allied ova having more 

 than once been mistaken for it. This rarity may be due 

 either to its tendency to sink, after a time, to the lower regions 

 of the water, or to the distance of the spawning-grounds from 

 the coast. The ripe season would seem to extend from the 

 beginning of June to the end of July at least, and probably 

 overlapping both periods. 



The ripe ovum of the turbot has an average diameter of 

 1"0287 millim., and the single oil-globule it contains measures 

 21 millim.* On extrusion the healthy ova are perfectly 

 buoyant, floating at the surface of still water or suspended in 

 mid-water. In some instances, however, at Danbar many of 

 the eggs went to the bottom, probably because changes had 

 occurred by long retention in the ovaries. The capsule {zona 

 radiata) is very distinctly wrinkled both in the fertilized and 

 in the unfertilized condition, indeed quite as much as in the 

 lemon-dab. The oil-globule presents no special tint, and 

 retains a nearly uniform diameter in all the specimens, as 

 Mr. Holt has already noticed. When the eggs were in mass 

 the latter observer was of opinion that the oil-globule gave a 

 faint ochreous hue to the whole. Like other forms these ova 

 are sensitive in the early stages and with difficulty bear a 

 journey, especially in warm weather, and it would be well in 

 such cases to delay transmission until the blastopore has 

 closed. 



Ova fertilized at 6 A.M. on the 22nd June were in the 

 multicelled condition at 6 P.M., but the disk showed certain 

 peculiarities, the result of the journey by rail from Dunbar to 

 St. Andrews in glass vessels, thick earthenware jars being 

 much better for transport. Thus many of the marginal cells 

 of the disk were much elevated and the nuclei clearly defined 

 as slightly pinkish bodies by transmitted light. Numerous 

 free nuclei were in the periblast. It seemed as if a somewhat 

 abnormal activity, due to external conditions, had ensued, 

 a view the more probable since the entire series perished 

 before next morning. 



Another series of ova, fertilized on June 21st at 5 P.M.^ and 



* Wenkebacli gives tlie diameter of tlie egg as 'To {Jide Cunningham). 



