Freshwater sponges, hydroids & polyzoa / by N. Annandale.

  • Nelson Annandale
Date:
1911
Catalogue details

Licence: In copyright

Credit: Freshwater sponges, hydroids & polyzoa / by N. Annandale. Source: Wellcome Collection.

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    phenomenon may be due solely to our ignorance of the occurrence of obscure genera or species in localities in wbicb tbey have not been properly sought for, or it may have some real significance as indicating that certain forms cannot always increase and multiply even in those localities that appear most suitable for them. As an example of universally distributed species we may take the European polyzoa of the genus Plumatella that occur in India, while of species whose range is apparently discontinuous better examples could not be found than the sponges Trochospongilla pennsylvanica and Spongilla crateriformis, both of which are only known from N. America, the British Isles, and India. My geographical list of the species of sponges, ccelenterates, and polyzoa as yet found in fresh water in India is modelled on Col. Alcock’s recently published list of the freshwater crabs (Potamonidae) of the Indian Empire *. I follow him in accepting, with slight modifications of my own, Blanford’s physiographical rather than his zoogeographical regions, not because I think that the latter have been or ought to be superseded so far as the vertebrates are concerned, but rather because the limits of the geographical distribution of aquatic invertebrates appear to depend on different factors from those that affect terrestrial animals or even aquatic vertebrates. “ Varieties ” are ignored in this list, because they are not con- sidered to have a geographical significance. The parts of India that are least known as regards the freshwater representatives of the groups under consideration are the valley of the Indus, the lakes of Kashmir and other parts of the Himalayas, the centre of the Peninsula, and the basin of the Brahmaputra. Those that are best known are the districts round Bombay, Calcutta, Madri^ and Bangalore, Travancore and Northern Tenasserim. Little is known as regards Ceylon, and almost nothing as regards the countries that surround the Indian Empire, a few species only having been recorded from Yunnan and the Malay Peniusula, none from Persia, Afghanistan, or Eastern Turkestan, and only one from Tibet. Professor Max 'W eber’s researches have, however, taught us something as regards Sumatra and Java, while the results of various expeditions to Tropical Africa are beginning to cast light on the lower invertebrates of the great lakes in the centre of that continent and of the basin of the Nile. ♦ Cat. lud. Dec. Crust. Coll. Ind. Mus., part i, iasc. ii (Potamonid®), 1910.
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