In a move that will increase its capacity by about 50 percent, Carnival Cruise Lines Inc. has agreed to purchase four cruise vessels and hotel and land tour operations from Holland America Line N.V. for $625 million. The deal will reinforce Carnival's status as the world's largest cruise operation in terms of passengers. Carnival Cruise Lines' seven cruise ships have a total of 8,500 berths and typically operate at full capacity, which has led the Miami-based company to scramble for increased capacity through acquisitions and an aggressive construction program. The Holland America ships will not solve Carnival's capacity woes in its basic Caribbean business since Holland America's Alaskan cruise trade is too profitable to disrupt. Complementary Operations