178 B. W. PRIEST ON THE STATOBLASTS OF 



Taking Parmula Batesii as the typical species, we shall see that 

 the Statoblast, besides being a beautiful object when magnified, is 

 very curious in the arrangement of its spicules. 



It is large, globular, and more or less tuberculated. Crust very 

 thick, composed of micro-cellular structure, which grows out through 

 the interstices of the reticulated arrangement of the skeleton spicules, 

 and forms somewhat of a capsular covering to the Statoblast, as 

 in Titbella, giving it the tuberculated appearance just mentioned. 

 It is charged with, and surrounded by minute, thin, curved, fusi- 

 form, gradually sharp -pointed, spinous acerate, spicules irregularly 

 dispersed through the substance, limited, both inside and outside, by 

 a layer of parmuliform spicules, the former in contact with the 

 chitinous coat, and the latter on the free surface of the crust, giv- 

 ing it a light-brown colour. 



The parmuliform spicule is circular, flat, infundibuliform, ter- 

 minating in a point, like a little round shield turned up at the 

 margin, which is even. The spicules are arranged both internally 

 and externally in the Statoblast in juxtaposition, more or less 

 overlapping each other with the funnel-shaped process outwards in 

 both instances, so that the surface is covered with little points. 



The Sponges comprising Tubella and Parmula possess an ex- 

 tremely rigid reticulated structure, as also the next and last genus, 

 Uruguaya, so named from having been found in the rapids of the 

 river Uruguay. The only species is U. corallioides of which the 

 Statoblast has not yet been discovered; 



Dr. Dybowski has, I believe, found Sponges in Lake Baikal, in 

 Central Asia, including a new genus, Lubomirslda, comprising 

 four species with their varieties, but the Statoblasts were absent in 

 all of them. 



Without taking these into consideration, we have thus five genera 

 of Freshwater Sponges, including 24 species, in only one of which 

 the Statoblast is unknown. Two only of these have been found in 

 the British Isles, varying in structure according to locality, &c. It 

 would not surprise me if other species should be found some day, 

 particularly as they seem to have existed in former years in larger 

 numbers of species, as proved by the presence of the amphidiscs 

 and spicules found in freshwater deposits, many of which are differ- 

 ent in form from those at present known. 



Referring to what I stated at the commencement of this paper, 

 that Statoblasts do not occur in any known Marine Sponges, I have 

 been asked occasionally, " What then do you call the bodies found 



