IF in his' domestic habits man makes himself and his animals and plants an easy prey to parasites, as Professor Tattersall has explained in his previous talks, he works havoc on a far wider scale when he travels about the world.
Organisms that are harmless in their own environment may become deadly when transplanted, and in the last of his talks, Prof. Tattersall will describe how this has happened in many instances, such as the famous example of the rabbits that are one of Australias chief pests.