Lear Corp.'s (NYSE:LEA) shares surged as much as 15% Monday, rallying after the auto-parts supplier said billionaire financier and top shareholder Carl Icahn has made an offer to buy all of the company's outstanding stock. Lear's stock finished up $3.97 at $38.64 after notching a 52-week high of $39.88 earlier in the session. The $36-a-share offer from Icahn represents a 3.8% premium over the stock's Friday closing price. Icahn currently holds nearly 12 million shares of Lear, which amounts to 17.8% of the total. He bought into the company with a $200 million stake in October, when the stock was trading below $25 a share.

Argonaut Group Inc. (NDAQ:AGII) shares rose 5.2% Monday after the company reported Q4 earnings of $31.4 million, or $0.92 a share, up from a year-ago profit of $25.4 million, or $0.76 a share. Total revenue rose 14.5% at the San Antonio specialty insurer in the three-month period to $243.1 million from $212.4 million in the same period a year earlier.

Asyst Technologies Inc. (NDAQ:ASYT) shares climbed 6.3% after the company was upgraded to buy from neutral at American Technology Research.

Cognizant Technology Solutions Corp. (NDAQ:CTSH) shares rose 8.3% after the company said their Q4 net income rose 21% to $69.5 million, or $0.46 a share, from $57.7 million, or $0.39 a share, a year ago. Q4 revenue rose 65% to $424.4 million from $256.9 million. It is estimated that the company will earn $0.43 a share on revenue of $405.5 million for the latest Q4.

Hanover Compressor Co. (NYSE:HC) shares surged 18% while shares of Universal Compression Holdings Inc. jumped 16% after the companies announced their boards have approved a merger that will create a combined company with a market capitalization of $3.8 billion.

Herbalife Inc. shares soared 21% after the company said it has received an acquisition offer of $38 a share from Whitney V L.P. and its affiliates. Whitney and its related parties already own roughly 27% of the Los Angeles-based vitamin and nutritional supplement company's outstanding stock. Herbalife said it has formed a special board committee to review the offer.

Rambus (NDAQ:RMBS) shares soared 24% after the Federal Trade Commission ordered the company to license some of its older computer memory-chip technology and set maximum royalty rates it can collect for licensing.

Shares of The Mills Corp. (NYSE:MLS) surged 16% after Simon Property Group Inc. and private equity firm Farrallon Capital Management LLC disclosed a joint proposal to acquire the company for $24 per share. At present, Mills has an agreement in place to be acquired by Brookfield Asset Management Inc. for $21 per share. Farralon manages funds that currently own roughly 10.9% of Mills' outstanding common stock.

Columbia Laboratories' (NDAQ:CBRS) shares plummeted 68% after the Livingston, N.J.-based company announced that its Phase III clinical trial of progesterone for the prevention of preterm birth did not achieve any reduction in the incidence of preterm birth at week 32, the primary endpoint.

NewMarket (NYSE:NEU) shares fell 18% after the Richmond, Va.-based maker of chemical additives late reported Q4 net earnings of $4.5 million, or $0.26 a share, down from $11.1 million, or $0.64 a share, in the year-ago period. Revenue rose to $306.2 million from $293.7 million.

Royal Caribbean Cruises (NYSE:RCL) shares fell 5.1% as investors focused on a tempered 2007 outlook and looked past the cruise-line operator swinging back into the black during Q4.

Transmeta Corp. (NDAQ:TMTA) shares tumbled 11% after the company said it's streamlining its operations to focus on its core business of intellectual property licensing. The company plans to decrease its workforce by roughly 39% as part of the restructuring, shedding about 75 employees, mostly in its engineering services businesses.

State Street Corp. (NYSE:STT) shares lost 6.5% after the company said it plans to buy fellow Boston-based Investors Financial Services Corp. for about $4.5 billion in stock.  

SLM Corp. (NYSE:SLM) shares tumbled 8.8% after the White House proposed a 50-basis-point cut in student lender rate subsidies and increasing lender risk as part of a plan to save the government $95 billion in entitlement spending by 2012.

Natural gas for March delivery closed up 2.1%, adding 15.8 cents to close at $7.634 per million British thermal units on the New York Mercantile Exchange, after the contract reached as high as $7.93 in earlier dealings. Overnight, prices rose past $8 to their highest level since Dec. 14.

Hitachi Ltd.'s (NYSE:HIT) Hitachi Data Systems unit announced that it intends to buy Archivas Inc. for undisclosed terms. The Tokyo electronics company's unit said Archivas, of Waltham, Mass., makes software that allows user to store, protect and manage fixed-content data, such as document, email, database, image and audio files, in order to meet corporate governance, legal discovery and compliance regulations.