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. 



