BARNACLES. 201 



sets under water, and the animal is henceforth im- 

 movable. 



It now moults its skin once more. Another great 

 change takes place; the bivalve shell is thrown off, as are 

 also the eyes with their bent supports, and it is seen to 

 be a true Barnacle, though as yet of minute dimensions, 

 and with its valves in a very rudimentary condition. 

 It is now the representative of a third type among the 

 Crustacean forms, for it is in effect a Stomapod;* such 

 as the Opossum Shrimp (Jfysis), for example, with the 

 shield composed of several pieces, stony in texture, on 

 account of the great development of their calcareous 

 element, and so modified in form as to make a low cone, 

 the legs (become the cirri, or what I have above called 

 the "fingers") made to perform their movements back- 

 wards instead of forwards, and the whole abdomen 

 reduced to an almost invisible point. 



Marvellous indeed are these facts. If such changes 

 as these, or anything approaching to them, took place in 

 the history of some familiar domestic animal, — if the 

 horse, for instance, were invariably born under the form 

 of a fish, passed through several modifications of this 

 form, imitating the shape of the perch, then the pike, 

 then the eel, by successive castings of its skin ; then by 

 another shift appeared as a bird ; and then, glueing 

 itself by its forehead to some stone, with its feet in the 

 air, threw off its covering once mote, and became a foal, 

 which then gradually grew into a horse; — or if some 

 veracious traveller, some Livingstone or Earth, were to 

 tell us that such processes were the invariable conditions 

 under which some beast of burden, largely used in the 

 centre of Africa, passed, — should we not think them 

 very wonderful 1 Yet they would not be a whit more 



* From the Greek aro\ia (stoma'), mouth, and ttovc (pons), foot. A 

 name given to those Crustaceans which have proper feet near the 

 mouth. 



