340 M. Weltnev on the Survival o/" Spongillee The following table will serve to show how Sc. valida^ Lucas^ may be distinguished from the allied South-American species, which agree with it in possessing spines upon the femora of the nineteenth and twentieth pairs of legs and a deep transverse furrow upon the first dorsal plate : — A. Sternites smooth, not bisulcated; patellae of anal legs armed with spines prasina, C. Kocb, S. Amer. B. Sternites bisulcated. a. Last tergite with a median longitudinal crest viridicornis, Newp. S. Amer. b. Last tergite without a median longitudinal crest. a. Femora of all the legs armed ; patella of anal leg armed giy^^s. Leach. S. Amer. b. Femora of nineteenth and twentieth pairs of legs armed ; patella of anal leg unarmed valida, Lucas. N. Afr. XLI. — On the Survival of Spongillse after the Development of Swarm-larvas. By M. Weltner*. The assertion made by Laurent (1844) that our freshwater sponges perish after the development of swarm-larvge was disputed by Lieberkiihn (1857). Marshall (1884) supposes that there is an alternation of generations in Spongilla lacus-tris. From the gemmulai which live through the winter there originate in the spring male and female Spo^igillce which fertilize one another. The males die after the development of the semen ; the females, after the coming forth of the larvse, become neuters and perish in the autumn with formation of gemmules. The oftspring of the male and female specimens remain neuters in the first year and likewise break up into gemmules in the autumn. Gotte (1886), on the contrary, is of opinion that reproduc-tion universally causes the death not only of the Spongilloe^ but of sponges in general. The parts aft'ected by the repro-* Translated from a separate copy of the paper in the 'Sitzungs-berichte der Gesellschaft naturforschender Freuude zu Berlin/ February 21, 1888, pp. 18-22, communicated by H. J. Carter, F.R.S.
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