SPONGES. 89 



Spongia attenuata. — Plate XXII. 



This subject was found in a pond by the roadside, near Craigleith, 

 in August 1838. 



This substance, I understand, invests stones, and separates in a stra- 

 tum of an eighth of an inch in thickness. It is of a dingy yellow colour, 

 much resembling a piece of chamois leather. 



Numerous whitish spherules are dispersed throughout the substance. 

 When suspended in water, they swim moderately, with a revolution in 

 a vertical axis. 



Plate XXII. 



Figs 1.-17. Spongia attenuata. 



