334 VIEW OF NATURE. 



shells of the oyster and lobster are produced, or as nails grow 

 upon the fingers and toes of the human body. The quantity 

 of this carbonate of lime elaborated by the little coral animal 

 is truly wonderful ; islands are formed, and harbours blocked 

 up by it. Fig. 133, a, represents a branching coral ; the dots 

 show the apertures by which the animal receives its nourish- 

 ment. Some of the zoophites are fixed by a kind of root, to 

 the bottom of the sea ; some, as the sea-nettle, which appears 

 like the segment of a circle, are carried about by the motion 

 of the waters, without any voluntary motion, as, are also the 

 sea-daisy, sea-marygold, and the sea-carnation, so named from 

 an apparent resemblance to those plants. We find here the 

 sea-fan, the sea-pen, and the madrepore, the latter of which 

 are often thrown together in vast quantities. 



The sponge also belongs to this class of strange animal sub- 

 stances ; it consists of a fibrous mass, containing a jelly-like sub- 

 stance, which, when touched, discovers a slight sensation, the 

 only sign of life manifested by it. There are many species of 

 sponge ; those most valued in the arts are found in the Medi- 

 terranean sea and Indian ocean. Some grow upon rocks, and 

 are found covering the interior of submarine caves. The 

 Spongia parasitica is seen growing upon the back and legs of 

 a species of crab ; sometimes as many as forty individual 

 sponges extend themselves over the crab, impeding the motion 

 of its joints, spreading like a cloak over its back, or forming 

 for its head grotesque and towering ornaments, from which 

 the poor crab vainly attempts to disencumber itself. 



Some species of the sponge grow to a very large size ; one 

 has been found in the East Indies in the form of a cup, capable 

 of containing ten gallons of water. The fibrous part of the 

 sponge is the skeleton of the animal ; the large apertures (see 

 Fig. 133, &,) serve to carry out fluids from within ; while the 

 water by which the animal is nourished, is imbibed by minute 

 pores ; this continual circulation of water is one of the most 

 important functions of the living sponge. 



These animals resemble plants in their manner of producing 

 others ; they form a species of germ, like the bud growing 

 upon the stalk ; this foils off from the stem, and becomes a per- 

 fect animal. If a part of one of those animals is separated 

 from the rest, it will itself be as perfect a living animal as 

 was the whole before. A polypus can be divided into as 

 many animals as it contains atoms ; some of this order are very 

 properly called hydras (many headjed). Besides these, there 

 is another order of animal substances, infusoria, which appear 



Various kinds of zoophites Sponge manner in which these animals are 

 reproduced. 



