BARNACLES AND ACORN-SHELLS. I7Q 



order (Cirripsdia) by themselves. No wonder if you hesitate 

 to accept this statement as a fact ; you are in good company, 

 for no less a naturalist than the great Cuvier failed to see the 

 relationship. 



That this order is an important one will appear when it is 

 stated that the great Charles Darwin wrote an important 

 work in two volumes, devoted to the " recent " Cirripedes, 

 and two other volumes on the " fossil " species of the order. 



These Cirripedes are divided into two main groups the 

 pedunculated or stalked Cirripedes, represented by the lively 

 Barnacles before us, and the sessile or stalkless Cirripedes, of 

 which the familiar Acorn-shell of the littoral rocks are the 

 examples. 



Now these two groups may strike you as having little in 

 common, and yet their early history is practically identical, 

 one group with the other. Longfellow was quite right when 

 he stated that " things are not what they seem," at least, they 

 are not always what they seem ; conversely, they do not always 

 seem what they are. We must not be content with taking a 

 couple of creatures at one particular stage in their existence, 

 and say these organisms differ so widely from each other that 

 we must put them into equally widely separated classes or 

 groups ; we must try to find out and compare all the stages 

 in their life-histories, before we can talk of separating or 

 bringing together, except in the most temporary fashion, there 

 to be kept, as it were, in quarantine until we have found out 

 what we wish to know concerning their antecedents. 



No one, until he had evidence of the successive stages in 

 the life of a butterfly, would dream of putting such dissimilar 

 things as a caterpillar and a butterfly into the same order ; 

 yet their wonderful course of development was long ago 

 traced out, and it is within the power of any person to check 

 off the whole progress from the batch of elegant eggs laid on a 

 cabbage leaf, through the ravenous worm-like caterpillar stage, 

 and the apparently inanimate chrysalis to the beautiful white 



