174 B. W. PRIEST ON THE STATOBLASTS OF 



The reason assigned for the Statoblasts occurring only in the 

 Freshwater and not in the Marine Sponges is, that the former are 

 often left high and dry for weeks, perhaps for months together, 

 whilst the sea is constantly returning to cover the latter, they 

 therefore do not require the protection to the ova from the influence 

 of the atmosphere and other causes that the Freshwater Sponges 

 would do. 



The Statoblasts may be found most abundantly at the base of the 

 sponge towards the autumn or winter, but in the warm summer 

 days they are plentifully diffused throughout the entire body of the 

 sponge, excepting, perhaps, quite the new growth. 



The late Dr. Bowerbank placed the Spongilla under the genus 

 Isodictya, on account of the skeleton structure agreeing so perfectly 

 in the form of the spicules composing it, though distinguished from 

 that genus by the peculiarities of the reproductive organs, viz., the 

 Statoblasts, the Spongilla reproducing its kind after the manner of 

 the Marine Sponges, that is to say, by ova proper, and division of 

 the sarcode. 



The two British species were the only ones known as Fresh- 

 water Sponges, until, in 1848 and 1849, Mr. Carter published his 

 interesting "Memoirs on the Sponges found in the Bombay Tanks," 

 which memoir will be found in the " Annals of Natural History" of 

 those dates. Since then new forms and varieties have been met 

 with in Europe, Asia, and America, but strange to say, none have as 

 yet been brought from Africa, although no doubt they exist there. 



Describing the Statoblast generally, it is about the size of a large 

 pin's head, varying in this respect not only with the species, but in 

 the individual, and can be seen with the unassisted eve. 



In form it is more or less globular or oval, having a foramen or 

 hilum, either lateral or terminal on the surface, generally at the 

 bottom of an infundibular depression which leads to the interior. 



If we make a vertical section with a sharp, thin knife, through the 

 aperture of one of these bodies when dry, we shall observe that it 

 consists of an internal globular cavity, rilled more or less with a 

 soft waxy substance, of a yellowish colour, which substance, when 

 swollen out in water, will be found to be composed of a great 

 number of thin transparent sacs, somewhat spherical, filled respec- 

 tively with minute germinal matter, consisting of transparent germs 

 of different sizes, the whole enclosed by a delicate investing mem- 

 brane, slightly protruding at the aperture, and presenting a reti- 



