Dr. A. Wierzejski on Freshwater Sponges. 299 



as indeed is easily seen from the structure of the completely 

 formed mass. 



Passing to Dr. Vejdovsky's statements, I will, in the first 

 place, venture to make some remarks upon his revision of the 

 known European Spong-illida3 *. 



Tliis naturalist accepts only eight species as so-called good 

 species, and these he distributes in four genera. In ray 

 judgment the specific rank of Euspongilla rhenana, Retzer, 

 must also be regarded as doubtful. It is indeed sufficiently 

 characterized by the perfectly smooth coating-spicules bent 

 at the ends ; but I suspect that these structures are abnormal ; 

 for among the tuberculate coating-spicules of Euspongilla 

 lacustris, I have often found perfectly smooth crooked ones of 

 different lengths. 



Moreover, I possess two forms with such unusually deve- 

 loped siliceous elements in the shell of the gemmule that upon 

 this ground alone they might be designated as new species, 

 if certain considerations did not witness in favour of abnormal 

 development. 



In my catalogue of the Gallcian species f I have cited the 

 species Epliydatia Millleri^Li. & K., under the name of Meye- 

 nia Miilleri, chiefly on account of its histological structure, in 

 which it differs from all the species known to me, and there- 

 fore merits being placed in a separate genus. Thus the soft 

 body of this sponge consists of the histological elements and 

 organs which have been well known since Lieberkiihu's time, 

 and of vesicular cells. The latter agree morphologically with 

 the structures which have long been known in marine sponges, 

 which O. Schmidt has described in two species of Esperia, 

 and most appropriately compared with masses of soap-bubbles. 

 Portions of tissue in which these are particularly accumu- 

 lated remind us, as Vosmaer J correctly remarks, of the vesicular 

 connective substance of Leydig, and of the tissue of the 

 mantle of the Tunicata. In Mei/enia Miilleri they lie closely 

 approximated, especially in the dermal layer, and arranged 

 in several layers, more particularly in the neighbourhood of 

 the oscula ; but they are also to be met with throughout the 

 mesoderm, where they occur in greater or less number in 

 different periods of the life of the stock. In the fresh state 

 they are limpid spheres, in which we always detect a round 

 vesicle, the nucleus, and further minute, very brilliant gi-an- 

 ules in variable number, and different sized portions of a 



* See ' Annals,' he. cit. 



t See "Ogabkach slodkowodnych galicyskich." Krakow, 1885. 

 (Spraw. Kom. Fizyogr. Akad. Umietei', torn. xix.). 

 t lirouu, ' Kladsen und Ordnuugeu,' i'orif era. 



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