Stkphens — The Fresh-water Sponges of Ireland. 229 



well as smooth spicules occur, it may usually he taken that the writer does 

 not distinguish between E.fluviatilis and the closely allied species E.Mulleri. 

 For example, the majority of forms described by Potts (33) under E.fluvia- 

 tilis are really E. MiillcrL Waller (50), writing on the varieties of E. flutia- 

 tilis, describes a series of English specimens. The first three specimens 

 described, and their spicules figured, are typical E. Mulleri, with smooth 

 and spined oxea and short amphidiscs. The remaining two are typical 

 K. fluviatilis, with smooth oxea and longer amphidiscs. But the presence of 

 minutely spined megascleres in E. fluviatilis (as distinguished from E. Mulleri) 

 has been noted from time to lime by several writers, and the occurrence of 

 these spicules has sometimes been considered as an important character for 

 the establishment of new varieties. Vejdovsky (49) alludes to small, 

 slightly spined oxea in specinaens of E. fluviatilis from Bohemia. Topsent 

 (48) notes the occurrence of microspined oxea in a specimen from the liiver 

 Vesle, and in the same paper quotes 'J'raxler (" Foltdani Kozlony," xxv, 

 1895) as having observed similar spicules in the species. He also describes 

 (48) spined oxea as being abundant in his E. fluviatilis var. syriaca, from 

 the Eiver Barada, near Damascus and from Lake Huleh in Syria. Kirk- 

 patrick (22) describes them in his E. fluviatilis, var. capcnsis, from South 

 Africa, and Annandale (7, 9), in his E. flunatilis, sub-sp. himalaycnsis, from 

 the Western Himalayas. Weltner (54) refers to the presence of microspined 

 spicules in European examples of E. fluviatilis, and in specimens of the same 

 species from Turkestan (55). 



With regard to the specimens of E. fluviatilis, obtained in Ireland, a careful 

 examination shows that almost every spicule-preparatiou contains a few, in 

 most instances very few, microspined megascleres. In some cases, generally 

 when the spicules are fairly thick, the spination is very obscure, so that 

 the spicules, even under a high power of the microscope, appear to be merely 

 roughened. In other cases, geneially when the spicules are slender, the 

 spines are well developed, and often quite numerous. Tlie thicker micro- 

 spined oxea of the varieties syriaca and himalnyeiisis, just alluded to, and the 

 more slender oxea, with minute, sharp spines, of the variety capcnsis are 

 exactly similar to the spined oxea to be seen in various Irish specimens of 

 E. fluviatilis. The slender spicules appear to have more tendency to be 

 spined than the more robust ones. This is carried to an extreme, perhaps, 

 for the species in interesting specimens from the pond in the Zoological 

 Gardens, Dublin, in which many of the spicules, which are all rather slender, 

 are thickly covered with fairly strong spines (PI. XXVII, fig. 3). This 

 peculiarity was not limited to one specimen, but was seen in all the samples 

 collected in two successive years. The sponge was not abundant, and was 



