In his experiments to disprove the theory of spontaneous generation, Louis Pasteur used a swan-necked flask. One source implies that Pasteur invented it himself, but I haven't been able to find anything definite.
To address the criticism leveled at Spallanzani's early experiments, namely that boiling might destroy some "vital principle" in air, Pasteur devised a long swan-necked flask. Air could reach the flask through the opening but dust particles and microorganisms could not, because the curved neck served as a trap.