HGIC Harleysville Grp. Inc. (MM)

•    Share prices of commercial insurer Harleysville Group Inc. (NASDAQ:HGIC) rocketed up 87.06% to $58.96 after Nationwide Mutual Insurance Co. announced its decision to buy Harleysville for $1.63 billion

•    Analysts at Citi (NYSE:C) downgraded shares of dialysis-center operator DaVita Inc. (NYSE:DVA) from "Buy" rating to "Hold" rating

•    Shares of Family Dollar Stores Inc. (NYSE:FDO) dropped 4.35% after shareholder Nelson Peltz officially cancelled his $7.7 billion offer to buy the retailer

•    Semiconductor company Advanced Micro Devices' (NYSE:AMD) shares plunged 13.66% to close at $5.31 after the company lowered its guidance for the third quarter

•    Shares of retail drugstore chain Rite Aid (NYSE:RAD) gained 2% after the company said same-store sales have increased by 1.3% year-over-year for September. However, sales from front-end same stores dropped 0.5%

•    Analysts at Macquarie Shares initiated coverage on online game developer NetEase.com (NASDAQ:NTES) with an "Outperform" rating and a target price of $50

•    Analysts at Macquarie started coverage on shares of Perfect World (NASDAQ:PWRD) with a "Neutral" rating and a target price of $15

•    Analysts at Sterne Agee Shares initiated coverage on financial advisory firm Blackstone (NYSE:BX) with a "Neutral" rating and a target price of $15