When i trade stock i found some questions about "Dark order" which execute on the platform(ISE,ATTN).The Dark order is non-display on the quote,but i can use Edga to hit them,usually the volume is always big(such as "3000 D" printed on the TAS). I want to know does Direct Edge offer the dark order?If not,who offer these dark order and what is his purpose? How can i find the stock which have lots dark order? Any reply as Appreciate