126 EUSPONGIA. 



Spongla officinalis, C. v. Linuc, Systema Naturae (J 758). 



Spongia officinalis, P. S. Pallas, Elenchus Zoophytorum, p. 87 (1768). 



(Other synonyms will be found in the descriptions of the varieties.) 



In shape and size this species (the common bath-sponge) varies pretty 

 much, but it is, as a rule, not difficult to assign any given specimen to it if it 

 is a true E. officinalis. A glance at the figures given by F. E. Schulze {he. cit.) 

 will give an adequate idea of the range of form within this species. 



The varieties E. o. adriatica, E. o. moUissima, E. o. rotunda, E. o. lobosa, and 

 E. 0. dura are massive, attached by a broad base, or pedunculate, erect, club- or 

 cup-shaped. Cup-shaped forms are particularly frequent in the variety E. o. 

 moUissima. E. o. nitens and E. o. spinosa are low incrusting forms. E. o. irre- 

 gularis and E. o. exigua are irregularly lobose and branched ; and E. o. lamella 

 and E. o. perforata appear lamellar, frondose. The true bath-sponge does 

 not grow to a very large size. The ordinary specimens measure 100-250 

 millim. in their largest diameter ; the largest specimens I have seen are only 

 300 millim. broad. We never observe such gigantic specimens as in the various 

 species of Hippospongia, which are also used for bathing-purposes. 



The surface of the living sponge is covered with abundant small conuli, which 

 are in most of the varieties on an average 1 millim. high and 3 millim. apart. 

 They are generally broad, rounded, and blunt — often so much so that they 

 appear as more or less semi-spherical protuberances ; they never seem to be 

 high and slender. The conuli are particularly small in E. o. spinosa. Although 

 foreign bodies are generally pretty abundant in the skin, no special cortex is 

 produced. In E. o. spinosa a superficial reticulation of arenaceous threads 

 is observed. The appearance of the surface of dry skeletons is more 

 varied. We generally observe the whole of it covered very uniformly with 

 small conic, denticulate, villi-like processes, which are of uniform height and 

 which terminate in a continuous surface. E. o. rotunda, E. o. lobosa, and E. o. 

 dura are more smooth than the other varieties. Here the superficial villi are 

 particularly low, in E. o. lobosa only 0-3 millim. high, and sometimes altogether 

 absent in portions of the surface. The surface of E. o. irregularis appears 

 knotty, uneven, and much more irregular; whilst that of E. o. lamella is rather 

 irregular in consequence of the presence of concavities, about 5 millim. wide, 

 into which the oscular tubes open. Grrooves are sometimes observed on the 

 surface of the skeleton, which, according to P. E. Schulze, correspond to large 

 tangential canals belonging to the system of subdermal cavities ; these are 

 situated radially, and particularly well developed on the margin of the cup- 

 shaped forms of E. o. moUissima. 



The oscula are large and conspicuous in most specimens of the varieties 

 E. 0. adriatica, moUissima, and rotunda, in which they often attain (in skele- 



