OCEAN LIFE. 41 



eating the position of the articulation ; but the whole remains 

 unprotected by any hard covering until the next change of shell, 

 after which it appears in a proper case, being, however, still con- 

 siderably smaller than the corresponding claw on the opposite 

 side of the body, although equally perfect in all its points." 



CIRRHOPODA. 



"HOWEVER distinct in outward appearance, and even in their 

 internal economy, the creatures composing the primary divisions 

 of animated nature may seem to be when superficially examined, 

 closer investigation invariably reveals to the zoologist gradations 

 of structure connecting most dissimilar types of organization, and 

 leading so insensibly from one to another, that the precise bound- 

 ary-line which separates them is not always easily defined. The 

 Cirrhopoda, indeed, present a strange combination of articulated 

 limbs, united with many of the external characters of a Mollusk, as 

 will be at once evident from the examination of any species of Bar- 

 nacle, whether Sesile or pedunculated." "At first sight no two 

 objects can well be more unlike than a Barnacle and a Shrimp. The 

 former is inclosed in a true shell composed of many pieces united 

 either by shelly matter or by cartilage, which allow of the pro- 

 trusion and retraction of a hand of fine hairy filaments, the whole 

 permanently affixed to foreign objects either by a thick, flexible 

 stalk, or by a broad immovable base. The older naturalists as- 

 sociated these animals with the shell bearing MOLLUSCA, calling 

 them multivalves, and even up to very recent times they have 

 been considered as equally allied to the sub-kingdom just named 

 and to that in which they occur here. Mr. Charles Darwin, 

 however, in his admirable Monograph, has fully demonstrated 

 the close affinity which subsists between them and the CRUSTACEA, 

 of which he, indeed, considers them only a sub-division. I pre- 

 fer, however, to treat them as a class by themselves, believing 

 that the diversity between the groups is quite as great as that 

 which subsists between the CRUSTACEA and the ARACHNIDA, or 

 between the ARACHNIDA and the INSECTA. The Barnacle begins 

 life in a form exactly like that of a young Entomostracous Crus- 

 G 



