The French census uses the commune as the basis of its returns, and employs the following classifications in respect to communal population: (I) Total communal population.
At present, therefore, classifications of the Hydromedusae have a more or less tentative character, and are liable to revision with increased knowledge of the life-histories of these organisms. Many groups bear at present two names, the one representing the group as defined by polyp-characters, the other as defined by medusa-characters.
Delage and Herouard (Hydrozoa ) were the first to make an heroic attempt to unite the two classifications into one, to which Hickson (Hydrozoa ) has made some additions and slight modifications.
52), referable to the family Clavidae; a fact sufficient to Indi a cate the tentative character of even the most modern classifications of this order.
One of the best known classifications on these lines is that by Warming.1 Warming recognized and defined four ecological classes as follows: Hydrophytes.These live in a watery or wet substratum, with at least 80% of water.