Objects for the Microscope. 195 



jointed, in others the chambers of the cells are so distinct 

 that the sarcode body may be considered as compound, and 

 one tiny shell to contain a family, the members of which 

 have been produced as gemma? or buds, one from the other. 



The subject is still under investigation by scientific men, 

 therefore I shall not enter further into it, but recommend 

 the student, if desirous of further information, to read 

 1 Weaver's Abstract of Foraminifera ' in ' Annals of Nat. 

 Hist,,' 1 841 ; ' Williamson Trans. Micros. Soc.' vol. ii., 

 and 'Micr. Journal/ vol. i. ; also 'Carpenter on the 

 Microscope,' chap. x. 



The structure of the shell itself is various, some being 

 single-chambered (I agena, Miliolina, and Gromia) ; the 

 greater number are compound shells, with cells arranged 

 lengthwise, or circular, or spiral, all of them dotted with 

 numerous foramina, or holes, from whence they are named 

 foraminated shells. 



We should have at least three slides of these in our 

 collection : one of the mixed specimens, one of the beau- 

 tiful Cristellarea, or Operculina, and one of the siliceous 

 Foraminifera from the Barbadoes deposit. 



THE OPERCULINA 



is the best example of a compound shell, to show the divi- 

 sion into chambers ; it is like a tiny nautilus, and if we 

 saw the interior we should find each chamber separated 

 from the other by double walls, or septa, containing tubes, 

 and which give off lateral branches, and a network of minute 

 veins for circulation of fluid. A large syphon or tube 

 forms the margin of the shell, and is the medium of com- 

 munication between the cells. 



The cells of this Foraminifer being calcareous, are easily 

 dissolved by muriatic acid ; and a recent specimen may be 

 examined by placing it in a watchglassful of water with one 

 drop of strong acid, when, in a very short time, the shell 

 will dissolve, leaving the animal naked and perfect with 

 every mark of its habitation left upon its plastic body. 



On examining a mixed slide you will find that some are 

 starlike (Astoma), some in complex whorls (Cassidulina), 



