1889.] on the Life-Mstorij of a 3Iarme Food-Jish. 385 



marine food-fishes the eggs are minute glassy spheres which float 

 freely in the ocean. For a knowledge of this fact we are indebted in 

 the first instance to Prof. G. 0. Sars, of Christiania, a naturalist 

 trained from boyhood under a distinguished father, and who by a 

 fortunate appointment to a fishery post in Norway, was enabled to 

 discover that the eggs of the cod, haddock, and gurnard, floated in the 

 water, or, as we term it, were pelagic. He thus oj)ened up a new 

 field in the economy of the food-fisbes, which in a great maritime 

 country like ours ought not to have remained so long unexplored. 



Lately, however, attention has been earnestly directed to the 

 subject, and the labours of Cunningham, Brook, Prince, and others 

 have made considerable advances in this department. 



It is now known that the great majority of our British marine 

 food-fishes — indeed all our most valuable kinds (including even the 

 sprat and the pilchard amongst the clupeoids) produce minute eggs 

 (Fig. 1) — as transparent as crystal, and 

 which float freely throughout the water. Fig. 1.* 



These eggs, moreover, are not all shed at 

 once, as in the case of the salmon, but suc- 

 cessive portions of the ovary become ripe, 

 and the eggs then issue externally. If by 

 uny accident or irregularity — as for instance 

 the confinement of a flounder in an unhealthy 

 tank — this gradational issue is interfered 

 with, the animal dies from the great dis- 

 tention caused by the pent-up eggs. In the 

 case of the cod this gradual issue of the 

 eggs continues probably for a week or two, Pelagic egg of the Ling, 

 so that the progeny of a single fish in one enlarged, 



season may vary considerably in size. 



From the early months of the year onward to late autumn the sea 

 off our shores thus abounds with pelagic eggs, those of the rockling, 

 haddock, and sprat being amongst the earlier forms, while the later 

 include those of the sole. As indicated in the Trawling Report, and 

 now supported by further experience, it would be a very difficult 

 matter indeed to arrange for a close time in the sea, that is to say, for 

 a limited period during which the mature fishes might be permitted to 

 spawn in peace. This, however, in the case of individual species, 

 such as the cod, might more readily be carried out, so as to save the 

 mature fishes at the spawning period. 



In a vessel of still sea water these transparent glassy spheres 

 rise at once on issuing from the fish, and form a stratum on the 

 surface. Even the ripe portions of ovaries removed from the 

 rejected viscera on a j)ier will show the same features, and thus, 

 indeed, they first came before the lamented Lord Dalhousie at 



* I am indebted to Mr. E. E. Prince, B.A. for kindly aiding me with sketches 

 for the woodcuts. The sketch of Motella is by Dr. Scharff. When floating freely 

 in the sea the blastodisk is inferior. 



