It would be entering into too large and intricate a subject, and too technical a one, to attempt to discuss Polar invertebrate life in the present volume. It is also dangerous at the present time to formulate general statements regarding the distribution and general laws which regulate this host of living beings, as Polar exploration is as yet in its infancy, as far as serious research in this subject is concerned. Still there are one or two points that may already be gleaned from the oceanographical research of several of the recent expeditions to the Arctic and Antarctic—notably those of Leigh Smith, Payer, Nordenskjold, the Prince of Monaco, Duke of Orleans, Nathorst and others in the north, and those of the Challenger, Valdivia, Belgica, Scotia, Discovery, Gauss, Français, Antarctic and Pourquoi-pas? in the south.
One forecast of importance that may be made is regarding the theory of "Bipolarity," in which it is suggested that species of animals in Arctic seas find, as it were, their reflected images represented by species in Antarctic seas.
A few years ago the case was doubtful. But modern Polar exploration, especially in Antarctic seas, with the tendency to explore more thoroughly definite areas, by vessels carrying on board a much larger number and more highly trained staffs of naturalists, to whom
