18 GENERAL REMARKS ON THE EGGS OF MARINE FISHES. 



confined volume of water (e.g. in a small jar) is easily over- 

 looked by the casual observer. 



The appearance presented by a number of pelagic eggs 

 floating in sea water, like tiny pellucid bubbles, is not easily 

 forgotten, especially if they should happen to belong to one of 

 the species (e.g. Gurnard) which have inside the egg a glistening 

 little oil-globule which moves freely in the yolk. 



Condition of pelagic eggs. Pelagic eggs usually float 

 singly in the water, except in certain notable instances, e.g. 

 the frog-fish, in which the eggs are surrounded by a transparent 

 gelatinous substance having the form of a long riband, as first 

 described by Prof. Alex Agassiz. Prof. E. van Beneden also 

 found some minute isolated and agglutinated floating eggs 

 which he was not able to determine, and Prof. Haeckel 

 procured similar eggs off the coast of Corsica 1 . Such eggs 

 differ from the pelagic nests of the Sargasso sea, with their 

 masses of fimbriated eggs as described by Louis and Alex. 

 Agassiz, J. T. Cunningham, Mb'bius and others, and which 

 belong to such fishes as Antennarius aod Pterophyrnoides, near 

 allies of the frog-fish. 



A marked translucency, in many cases almost perfect trans- 

 parency, of both capsule and contents usually indicates the 

 healthy pelagic egg. When developing in the ovary such eggs 

 are quite opaque, as observed in the " roe " on the fishmonger's 

 slab, but towards maturity the granules of the yolk disappear 

 and the ovarian egg becomes quite translucent. 



From observations made by Mr Harold Dannevig at the 

 Dunbar Fish Hatchery of the Fishery Board in 1884-5 the 

 pelagic eggs of the plaice, lemon-dab and other forms would 

 seem to be shed for the most part at night. 



When placed in a vessel of sea water the eggs persistently 

 float on its surface, descending but a very little when the jar is 

 rudely shaken. Even after a protracted journey only the dead 

 ones roll on the bottom of the vessel. All the floating eggs are 

 living. For instance, eggs removed from the cod and fertilized 

 on Smith Bank off Caithness, and even at 'a much greater dis- 

 tance, were carried to the Marine Laboratory at St Andrews, still 



1 Fierasfer? 



