190 NATURAL HISTORY OF OUR SHORES 



These embryos are about T^O of an inch in size, and 

 their number within one oyster is from one to two 

 millions. 



As they increase in size they begin to show the dark 

 line of the alimentary canal, and also develop a little 

 transparent shell, which has both valves convex. From 

 within the gaping edges of the shell extend two flaps, which 

 are fringed with cilia at their edges. The little oyster is 

 now in the veliger stage, and, in the language of the 

 trade, they form " black spat." Then when they are 

 sufficiently advanced they are shot forth in clouds into 

 the open sea. By means of their cilia they swim nimbly 

 and beautifully, the hinged side of the shell downwards, 

 at all depths. 



They continue in this veliger stage for from fifteen to 

 twenty-five days, and then settle down, and affix themselves 

 to some object ; but only a very small percentage have 

 the opportunity of so settling, for from the moment they 

 are cast upon the world the slaughter of the innocents 

 begins. 



" Nature red in tooth and claw " is still more red in 

 ciliated tentacle, sting cell, and suctorial mouth, and their 

 comrades in the world of waters jelly-fishes, from the 

 size of a pin's point upwards, pelagic worms, crustaceans, 

 larval fishes, and a host of other forms feed upon them, 

 and only a few survive. If it were not so, within a very 

 few years the world itself would not contain them. 



Those that so far have escaped disaster affix them- 

 selves, at first by means of their little flaps, then by the 

 secretion of lime, to any suitable surface. 



The surface, as we have said, must be clean and, pre- 

 ferably, gritty, although they will affix to wood, but where 

 there is mud or a layer of silt upon the objects they 

 cannot affix, and so perish. When first they can be seen 

 by the naked eye in the fixed condition they appear as if 



