78 MEMOIR IV. 



Under the foregoing impressions, some of them were 

 collected in the Spring of 1826. and in order to see what 

 changes they might undergo, were kept in a glass vessel 

 covered by such a depth of sea-water that they could be 

 examined at any time by means of a common magnifying 

 glass ; they were taken May 1st, and on the night of the 

 8th, the author had the satisfaction to find that two of them 

 had thrown off their cxuvia, and ^ronderful to say, were 

 firmly adhering to the bottom of the vessel and changed 

 into young Barnacles ! such as are usually seen intermixed 

 with grown specimens on rocks and stones at this season 

 of the year — (Balanus pusillus Pcnn.) In this stage 

 the sutures between the valves of the shell and of the oper- 

 culum were visible, and the movements of the arms of the 

 animal within, although these last were not yet completely 

 developed ; the Eyes also were still perceptible, although 

 the principal part of the black colouring matter appeared 

 to have been thrown off with the cxuvium. On the 10th 

 another individual was seen in the act of throiving off its 

 ahcll, and attaching itself as the others, to the bottom 

 of the glass. It only remains to add that as the secretion 

 of calcareous matter goes on in the compartments destined 

 for the valves of the shelly covering, the Eyes gradually 

 disappear, from the increasing 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 an animal originally natatory and locomotive, 

 and provided with a distinct organ of sight, becomes per- 

 manently and immovcably fixed, and its optic apparatus 

 obliterated ! and furnishes not only a new and important 

 physiological fact, but is the only instance in nature of so 

 extraordinary a metamorphosis. 



Having made manifest the mctamorjihosis in the 

 Cirripedes,and shown by the nature of the animal in its first 

 or larva state, that they are clearly referable to the class 

 of Crustacea, it may still be thought requisite to add the 



