BY R. VON LENDENFELD, PH.D. 289 



The ordinaiy shape of this species is that of a more or less 

 irregular bulb. (Plate XXVI., fig. 1), on which excrescences are 

 aften found, these may attain the digitate shape characteristic of the 

 variety represented in Plate XXVI., fig. 2. Often the bulbous 

 central mass disappears altogether, and the whole sponge consists 

 of a smaller or greater number — up to eight have been observed — 

 of finger-shaped processes of varying length. 



The finger-shaped pi'ocesses are cylindrical, and generally have 

 a very regular, circular transverse section. (Plate XXVII., fig. 5.) 

 Rarely the sponge expands in the shape of a flat lamella attached 

 by a small portion of the lower surface to suitable bodies in the sea. 



In outer appearance our sponge represents a species of Echispidse 

 very frequent in Australian waters, so closely that it is often hard 

 to tell the difference between them without microscopic investiga- 

 tion. It appears to me that this is a case of mimicry. The 

 Echispid Sponge referred to is filled with sharp and dangerous 

 spicules ti'. ac, and tr. tr., and it may be of advantage to the more 

 defenceless Halme Nidus Vesparum to imitate this better protected 

 sponge in external appearances to escape being attacked by some 

 ra})acious animal. 



Size. 



The largest bulbous specimens attain a diameter of 60 mm. 

 The finger-shaped processes of the other variety are genei'ally 

 about 12-18 mm. thick, and attain a length of 70-120 mm. 



The largest specimens I have seen belong to the digitate variety. 



Color, 



The sponge is gray with a slight violet tinge when alive. This 

 tinge vanishes as soon as the sponge dies, and is probably caused 

 by a fluorescence in the outer cells in a similar way as the beautiful 

 carmoisin red of the live Aplysilla violacea. (1) 



In spirits and dry, this sponge is gray, it has in fact the color of 

 the sand which forms the greater portion of its cortex. 



Color varieties have not been observed by me. 



(1) R.v. LendenfeM. Ueber Coelenteraten der Slidsee, Zweite Mittheilung. 

 Neue Aplysinidfe, Zeitschrift fiir wissenschaftliche Zoologie. Band 

 XXXVIII., Seite238. 



