_H. oligactis_ is usually a more vigorous form than _H. vulgaris_ and, in spite of its name, has often a considerable number of tentacles. The few Indian specimens examined have, however, been small and have not had more than six tentacles. I have not seen an Indian specimen with more than two buds, but European specimens sometimes produce a great many, and as the daughter buds do not always separate from the parent until they have themselves produced buds, temporary colonies of some complexity arise; Chun figures a specimen with nineteen daughter and granddaughter buds[AV]. [Footnote AV: Pallas writes as regards this "pulcherrime vegetantem varietatem" with his usual critical insight, "Vix tamen peculiaris speciei nomine salutanda videtur." It is probably the _Hydra socialis_ of Linné.] In Europe and N. America there appear to be two races or phases of the species. To avoid ambiguity they may be called form A and form B and described as follows:-- Form A is of vigorous growth. It is as a rule dioecious, and its reproductive organs may be borne practically at any level on the surface of the column. Its eggs are spherical and as a rule covered almost uniformly with spines. Form B is smaller and has smaller and more variable nettle-cells. Its reproductive organs are borne only on the distal third or at the base of its column and it is often monoecious. The lower surface of its egg is flattened, adherent, and devoid of spines. The larger form (A) was originally named _Hydra monoecia_ by Downing, who in 1904 expressed a wish to substitute for the specific name, which had been given through inadvertence, the more appropriate one _dioecia_. As, however, it appears to be the commoner of the two in northern Europe, we may regard it as probably being the one named _Hydra oligactis_ by Pallas and therefore may accept it as the _forma typica_ of that species. According to Brauer (1908) the smaller form is Linné's _Hydra polypus_; but the original description of the "species" hardly bears out this view. As reproductive organs have not yet been found in Indian specimens, it is impossible to say to which of the two forms they belong. A red form of _H. oligactis_ occurs in Tibet in the lake Rham-tso, at an altitude of about 15,000 feet and has been reported from various small lakes in mountainous parts of Europe. It is probably the form called _Hydra rhætica_ by Asper, but his figures are lacking in detail and appear to have been drawn from specimens in a state of partial contraction. _H. rubra_, Lewes (Ann. Mag. Nat. Hist. (3) v, p. 71, 1860), may also be identical with this form. Roux, indeed, states that _H. rubra_ is only found living unattached at considerable depths (Ann. Biol. lacustre ii, p. 266, 1907); but this statement does not accord with the fact that Lewes's specimens were found in ponds on Wimbledon Common. TYPE not in existence.