METAMORPHOSIS OF THE CIRRHIPEDES. 39 



only remains to state, that as the secretion of calcareous 

 matter goes on in the compartments destined for the 

 valves of the shelly covering, the eyes gradually disap- 

 pear, from the increased opacity thence produced, and 

 the visual ray is extinguished for the remainder of the 

 animal's life : the arms at the same time acquire their 

 usual ciliated appearance. Thus then/' continues our 

 author, " an animal originally natatory and locomotive, 

 provided at the same time with a distinct organ for 

 sight, becomes permanently and immoveably fixed, and 

 its optic apparatus obliterated." * The relation which 

 the above extraordinary discovery establishes between 

 the Cirrhipedes and the Crustacea is so intimate, that 

 Mr. Thompson, as will subsequently appear, considers 

 both as belonging to one class. We trust this indefa- 

 tigable and acute naturalist will himself prosecute the 

 interesting discovery here detailed, where he now re- 

 sides t : he has opened a vast field for research, as new 

 as it is important. We have yet to learn the metamor- 

 phosis of the pedunculated and diadem barnacles, the 

 larvae of which must have many peculiarities. The 

 few numbers of this gentleman's Zoological Researches, 

 which have yet appeared, are filled with new and im- 

 portant facts regarding the minute inhabitants of the 

 ocean, scarcely inferior in importance to that which 

 we have here detailed. J 



(33.) To illustrate the foregoing facts, we must refer 

 to Mr. Thompson's figures and explanations, which will 

 make the reader better acquainted with the above de- 

 scription of the young barnacle. The natural size 

 is not larger than a grain of cress seed. When mag- 

 nified, and viewed from above, the turgid appear- 



* Zool. Researches, No. iii. p. 76. 



f Dr. Thompson holds a high medical appointment in New South Wales. 



j Mr. Westwood, on the strength of his observations upon the " Egg of 

 one of the West India Land Crabs," calls in question the whole theory.of 

 Mr. Thompson ; as if " the egg of a land crab " was sufficient to set aside 



Classif. of Insects, Addenda to vol. i. 



D 4 



