l8o BY THE DEEP SEA. 



butterfly that can take no solid food, and which by depositing 

 another batch of exactly similar eggs, completes the cycle, 

 and so assures us we have made no mistakes in our observa- 

 tions. 



In a like manner we can watch the series of stages, utterly 

 unlike each other, through which a crab, a lobster, a shrimp 

 or a Barnacle passes before it attains the adult condition ; 

 and when we find the early forms of the Barnacle agreeing in 

 a very curious way with stages in the life-history of typical 

 Crustaceans, we are perfectly justified in grouping them in 

 the same class of animal life. We have, in fact, pierced 

 through the disguise with which some of the adult forms have 

 sought to hide their identity, and have found out their true 

 characters. 



It must be confessed that the course of development in 

 some of these creatures partakes of the character of what has 

 been termed " an Irishman's rise." In the case of the cater- 

 pillar and the butterfly, everybody recognises that develop- 

 ment is progress, that the butterfly is a higher being than the 

 caterpillar. But in others development spells retrogression. 

 Such is undoubtedly the case with the Cirripedes, and with 

 certain crustaceans which lead the life of parasites. The 

 course of development in the Barnacles and Acorn-shells has 

 been very succinctly stated by Darwin. 



" The larvae in the first stage have three pairs of locomotive 

 organs, a simple single eye, and a probosciformed mouth, 

 with which they feed largely, for they increase much in size. 

 In the second stage, answering to the chrysalis stage of butter- 

 flies, they have six pairs of beautifully constructed natatory 

 legs, a pair of magnificent compound eyes, and extremely 

 complex antennas ; but they have a closed and imperfect 

 mouth, and cannot feed: their function at this stage is to 

 search out by their well-developed organs of sense, and to 

 reach by their active powers of swimming, a proper place 

 on which to become attached and to undergo their final 



