298 Dr. A. Wierzejski on Freshwater 8po7iges. XXXVIIT. — Observations on Freshwater Sponges. By Dr. A. Wierzejski*. The notes on freshwater sponges, lately published in the ' Zoologischer Anzeiger ' (nos. 238 and 239) by F. C. Noll and Dr. Vejdovsky, lead me to make the following observa-tions : — As regards tlie new species, Spongilla glomerata, Noll, described in no. 238, I adopt Dr. Vejdovsky's opinion, who considers it identical with S.fragilis, Leidy f. M. Noll further states that he has found Spongilla fluvia-tilis, L, &K.,with both smooth and tuberculate spicules, and even with the latter predominating, from which he thinks it may be concluded that S. Miilleri, L. & K., might only be a variety of S.fluviatilis, L. & K. Although among a great number of examples of S.Jluviatilis, L. & K., which I have examined, I have never found a single one with tuberculate spicules, I will not cast any doubt upon the correctness of Noll's statement. Nevertheless [ regard his supposition as inadmissible, as the above-mentioned species are very well distinguished from each other by well-marked characters which remain constant in whole series of forms. For reasons to be stated below I even esteem S. Miilleri to be generically distinct from S.fluviatilis. It may also be mentioned in passing that Dr. Marshall three years ago expressed the opinion that forms with coating-spicules in the external envelope of the gem mules might pass over into forms with amphidisci in that layer. This suppo-sition is supported chiefly upon the structure of the gemmules of >S'. jordanensisj var. druliarformis^ Vejd. As early as the year 1884 I expressed doubts as to its correctness \. Now, in his most recent revision of the European Spongillidae Dr. Vejdovsky has given up both his new species 8. jorda-nensis and the new variety druliteformis — a hint that it is not advisable to found far-reaching hypotheses upon isolated discoveries. Finally, I would call M. Noll's attention to the fact that he has formed an erroneous conception of the development of the gemmule-mass of S.fragilis. The individual gemmules of the mass are developed, not, as he states, by division from unusually large deposits witliin the cellular cortical layer, but from special deposits, as I proved in the year 1884, and * ' Zoologischer Anzeiger,' no. 245, February 28, 1887, pp. 122-126. t See 'Annals,' February 1887, p. 168. X See ' Orozwoju pakow gabek slodkowodnych europejskich tucziei o gad. Sp. fragilis, Leidy ' (Krakow, 1881), p. 5.
BioStor
