14 Prof. F. Vejdovsky on Freshwater Sponges, 



anxious to convince myself as to the rank of the species in 

 question, as also with regard to its relationships with the 

 freshwater sponges occurring in Europe. As is well known 

 I have compared Spongilla sibirica with S. {Euspongilla) 

 jordanensis, while Carter has recently regarded it as identical 

 with Spongilla frag His, Leidy (S. Lordii, Bow.). From my 

 examinations and comparisons of the American species with 

 Spongilla sibirica, the latter proves to be really identical with 

 S. fragilis, Leidy; nevertheless, in the form observed by 

 Dybowski, some not unessential differences occur, to which I 

 propose to refer in the following remarks, and at the same 

 time to append some observations upon other freshwater 

 sponges. 



The specimens at my disposal are stated to be from the 

 river Danici, in the neighbourhood of Charkow, and usually 

 form small nodules 2-3 centim. in diameter ; whilst a small 

 irregularly triangular fragment represents a nearly flat 

 cushion-like plate, furnished with a large regularly circular 

 osculum and numerous smaller pores. At the surface of the 

 nodules and of the lamella I find no gemmules ; but, on the 

 other hand, the latter occur in the interior of the nodules in 

 great numbers and of two different forms and colours, 

 namely : — 



1. Pale whitish-yellow gemmules, which do not cohere, 

 but appear to be irregularly scattered in the tissue of the 

 sponge. The general form and structure of these gemmules 

 are the same as I have indicated in the case of the young- 

 gem mules of Euspongilla lacustris (see my memoir on the 

 freshwater sponges of Bohemia, p. 17, pi. ii. fig. 13). In 

 point of fact such an immature gemmuleof Spongilla fragilis, 

 Leidy (S. sibirica, Dyb.), agrees with that of Euspongilla 

 lacustris, inasmuch as it is quite naked, possesses a single 

 horny membrane, and at the superior pole is destitute of the 

 air- tube which is so characteristic of this species. Some- 

 what older gemmules indeed are still naked, but, at the pole 

 indicated, they bear around the process which is generally 

 regarded as an aperture a short, straight, somewhat inflated 

 tube, which later on curves like a horn and becomes completely 

 closed at the extremity. 



2. Among the pale-coloured gemmules we find now and 

 then, although rather rarely, an isolated brownish gemmule. 

 On the other hand, such gemmules, generally of a dark brown 

 colour, are present in great numbers united in groups of 

 three or more, usually of eight, thirteen, or fifteen, but some- 

 times of from twenty to thirty, completely enclosed by the 

 surrounding skeletal tissue of the sponge. In examining such 



