130 ASCIDICE, OR SEA SQUIRTS. 



to their mouths by currents in the water. They have 

 not the elegance of form of the Sea Anemones, but many 

 are painted with the most gaudy colours. Their inter- 

 nal structure is very simple, and connects them closely 

 with the division of Mollusca which form bivalve shells, 

 the tunic in the Ascidice being strictly analogous to 

 the shell of the Conchifer. Their metamorphoses have 

 been watched by several distinguished Naturalists, and 

 offer highly curious points in their history. In the 

 young or tadpole state, they are extremely active, 

 swimming about by rapid motions of the tail, till the 

 young creature finds a spot where he can take root. 

 Then the tail disappears, and grasping fibres, or roots, 

 spring from the body, which gradually assumes the 

 form and adopts the quiet life of the parent from 

 which it sprung. It is thus, by giving to the young 

 animal powers which she denies to the fully grown, 

 that Nature, in these and many other of the stationary 

 lower animals, provides for the proper dispersion of the 

 species. Among more perfect animals, it is the old 

 take care of the young, and provide for them : here we 

 find the young possess instincts which they lose at an 

 advanced period of their life. 



The Ascidice, which, because they are common and of 

 large size, I have instanced as examples of the tunicated 

 Mollusca, are simple animals, each creature living by 

 itself ; but I should give an imperfect idea of the class 

 if I did not allude to the compound Ascidians, animals 

 of similar structure, which yet live associated, or con- 

 nected together into a compound body, such as we have 

 already seen among the Zoophytes. These are very 



