12 I 2 OYSTERS, AND ALL ABOUT THEM. 



crowsilk as it is locally termed, is found to preserve its 

 colour in the river. 



The following is copied from Nature of May ist, 1890 : 

 At the meeting of the Royal Society of Queensland, July 

 i yth, 1890, Mr. W. Saville Kent presented some interesting 

 Notes on the Embryology of the Australian Rock Oyster 

 (Ostrea Glomerata). 



He mentioned that, in connection with the investiga- 

 tion of this subject, he had been carrying on a series of 

 experiments with the view of accurately determining the 

 influence upon the embryonic brood that is exercised by 

 the advent of fresh-water floods, or other sudden changes 

 in the salinity of the water. 



Some important results had been obtained from a 

 series of oysters recently purchased in the market ; a fully 

 matured male and female were selected for experiment. 

 Portions of milt and ova from these two individuals were 

 abstracted and commingled with precisely the same con- 

 ditions, and placed respectively in water of three different 

 degrees of salinity. 



The first admitted was placed in sea-water of the full 

 ordinary strength. In the second there were equal pro- 

 portions of salt and fresh-water, and in the third, one part 

 of salt-water to three of fresh. 



As a result, the ova placed in the equal admixture of 

 salt and fresh-water exhibited active vitality, and were 

 quickly speeding in their developmental career. Of the 

 ova placed in pure sea-water but few were fructified, and 

 these developed very slowly. Those finally placed in the 

 water containing only a one-fourth proportion of sea-water 

 were entirely deprived of life, and soon began to disinte- 

 grate. To this last circumstance Mr. Saville Kent called 

 special attention. It indicated, he said, the pernicious 



