446 Mr. E. E. Prince on the 



Dr. Hensen noted *, and congregate in scattered groups like 

 oleaginous globules, but show no tendency to adhere together. 

 They float freely and are carried about by the slightest cur- 

 rent in the surrounding water. In still water they often 

 congregate in masses and form layers, the uppermost stratum 

 being pushed to the surface by the buoyancy of those under- 

 neath. Usually, however, they occur sparsely scattered over 

 large spaces, and in the open sea, except in certain areas, 

 they are so widely dispersed as to be rarely procured. Their 

 buoyancy Dr. Walleni considers to be favourable to their 

 development ; and, in reference to the cod, when the eggs, 

 from the more exposed Norwegian spawning-grounds, are 

 (he says f) " carried away by currents to a calm and secure 

 place on the lee-side they will be hatched under favourable 

 circumstances, and the fry will find an abundance of hiding- 

 places and food along the coast." 



Fertilization. 

 Pelagic ova float near the surface of the water for some 

 hours ; but their buoyancy is aifected by various conditions, 

 especially adulteration of the sea-water surrounding them J. 

 If no spermatozoa come into contact with them, in from two 

 to eight hours, their translucency becomes impaired, and 

 decending to the bottom they assume a milky opacity, the 

 capsule becoming wrinkled and distorted. This is probably 

 the fate of vast numbers of pelagic ova in our seas ; and 

 Hensen §, indeed, found in the inner bay of Kiel quantities of 

 non-living ova of plaice and cod while dredging in 1881. 

 Unfertilized eggs of T. gurnardas occasionally assume a 

 bright pink colour, the cause of which has not been satisfac- 

 torily determined. 1'he minute vesicles and granules suspended 

 in the protoplasmic investment of the yolk persist for thirty 

 or forty minutes after fecundation and then slowly become 

 less abundant. The entrance of the spermatozoon was never 

 actually seen, although successive series of ova were prepared 

 and carefully watched in the laboratory, and active sperma- 

 tozoa were seen clinging to the external capsule ; but it is 

 probable that each ovum admits only one spermatozoon through 

 the micropyle. The fertilized ovum is readily distinguished 

 from those in an unimpregnated condition by its more trans- 



* U. S. Fish. Comm. Report, 1882, p. 434 ; see also Report of Royal 

 Comm. on Trawliug, 1884, p. 36. 



t Int. Fish. Exh. Lond. Confereuce Papers: 'Fish Supply of Norway,' 

 r. M. Walleni, p. 9. 



[ Vide ' Report of 11. M. Trawling Commissicm, 1884,' p. 3G2, and 

 ' Second Annual Report of Fishery 15oard for Scotland/ App. F, p. 47. 



§ U. S. Fish. Comm. Rep. 1882, p. 434. 



