604 Eadiata. 



merable small apertures or pores, communicating with a 

 network of fine canals, which permeate every part of the 

 substance and convey to the minute and simple creatures 

 which form the living part of this curious compound 

 animal, the food and water necessary for their support 

 and respiration. These fine canals unite into larger 

 passages, leading to orifices of considerable size usually 

 placed on prominences of the surface; from these the 

 water streams forth with such force, according to some 

 observers, as to be perceptible by the eye. 



The inherent chemical properties of this curious Zoo- 

 phyte are very remarkable. When a Sponge has been 

 immersed for fourteen or sixteen days in nitric acid 

 (diluted with three parts of distilled water) it becomes 

 nearly transparent, and when touched with ammonia, 

 assumes a deep orange colour, inclining to a brownish 

 red. But if much softened by the acid, the whole fabric 

 immediately disappears, on being immersed in ammonia, 

 and forms a deep orange-coloured solution. A Sponge, 

 when boiled, gives out a considerable portion of animal 

 jelly. The infusion of a small quantity of oak bark 

 causes this to fall to the bottom of the vessel, as a sedi- 

 ment, and so entirely changes the nature of the Sponge, 

 that, when dry, it crumbles between the fingers ; and, 

 when moist, it may be torn like wetted paper. In this 

 state we should naturally conclude that it is entirely 

 useless : but no ; the operations of chemistry resemble 

 a magic wand. Boil the same in water, with caustic 

 potash, its latent qualities will be called forth; and, 

 behold, a deposition of animal soap ! 



THE FRESH-WATER POLYPI AND THEIK 

 MARINE ALLIES. (Hydroida.) 



THESE are two species, which will fully illustrate the 

 nature of the whole tribe. They are found in clear 

 waters, and may generally be seen in small ditches and 

 trenches of fields, especially in the months of April and 

 May. They afiix themselves to the under-parts of leaves, 

 and to the stalks of such vegetables as happen to grow in 



