Professional staffing firm On Assignment Inc. beat earnings expectations in the third quarter thanks in part to the recent acquisition of a local competitor. The Calabasas company reported net income was up 139 percent to $17.4 million (33 cents a share), compared to $7.8 million (21 cents) in the same quarter a year earlier. Revenue was up 140 percent to $388 million, including contributions from Apex Systems Inc., a Long Beach staffing firm acquired in the second quarter. On a pro forma basis, excluding Apex, the company said revenue grew 14.3 percent. Analysts on average had expected net income of $15.6 million (30 cents) on revenue of $385 million, according to Thomson Reuters. Chief Executive Peter Dameris said the company showed strong organic growth despite the halting recovery. “I’m very pleased that despite the macro-economic challenges, we grew our revenues year-over-year,” said Dameris, in a statement. On Assignment places professional staff in the technology, life sciences and the health care industries. It has operations in North America, Europe and Australia. Shares closed down 39 cents, or 2 percent, to close Friday at $19.09 on the New York Stock Exchange.