Jupiter Communications, an online consultancy, acquired WebTrack Information Services, a publisher of newsletters and data on online advertising. Terms of the transaction weren't disclosed. Jupiter acquired the company from Caddis International, an investment company. WebTrack's InterAd Monthly newsletter and AdSpend database of Web ad spending will be added to Jupiter's existing portfolio of research services. Richard Tahta, Caddis president, will serve as non-executive director on Jupiter's board.