34 TOILERS IN THE SEA. 



performed no insignificant part in the history of the 

 world. For the present it will be sufficient to note 

 that they are brought up from the deep-sea bottom 

 everywhere, and that myriads of them are still living 

 in the ocean, even as myriads have flourished in the 

 seas of indefinable past ages. Many of these elegant 

 little shells are individually not to be distinguished 

 by the naked eye ; but they partake of a variety of 

 forms, some consisting of a single chamber, and 

 others of a great many, but in all, their composition, 

 like that of the oyster and cockle, is principally 

 carbonate of lime, such as we know it in chalk 

 and limestone, of which these shells are important 

 factors. 



Some of the shells consist of a single chamber, 

 others of several, and still others of a very consider- 

 able number. The many-chambered shells are at 

 first simple, or, as it seems probable with the rudi- 

 ments of two or three others, the greater part of the 

 chambers being added consecutively by a kind of 

 budding, the primary chamber being the smallest. 

 These chambers are not absolutely isolated, but the 

 walls, or divisions, are perforated, and through these 

 perforations there is a " continuity of protoplasm," a 

 union of all the segments of the compound body 

 which inhabits them ; so that in such species as do 

 not possess perforations in the external walls 

 of the shell, through which to extend their 



