(PI. I. II. IV. V.V. or. the cuirass wanting, the 

 epidermis is naked (PI. III. et VI.)- 



The cuirass, answering, in the greatest number 

 of animalcules, to the \alve of muscles, is composed 

 of (no siliceous and transparent part*, surrounding 

 the animal. The uimahe cuirass is a leaf rolled on 

 itself (Fie:. ;>-17., ;ts--m, the edges of which 

 are confounded together, so that they ne>er form, 

 except a few small openings, a >alve surrounding 

 entirely the animaleule. That cuirass appears smooth, 

 for instance, in the Frustulia appemlicttlata. Ag. 

 (PI. 1. fu-. U' 13. a.\ or striped, as in the A'arri- 

 ruta coslata (PI. I. fig. 9 110, where the stripes 

 are distributed like ra\ s, setting from an ombilie, to 

 be found in one of tiie middle ribs of the cuirass 

 i. !>. a.V, or merely ribbed: or pnnidod uith 

 Mroii and eloated ribs, such as in the iVflrrJftffa 

 ciliata (PI. I. fig. 5. aO, where the ribs arc besides 

 co> ered \\ ith line hair. 



-.rds the lo^er parts, the cuirass forms in 

 the Xariculat and Frustuliae a tint sm -face, jrenerallv 

 qurtdraiiirular ( parallelogram! , called pt'iittl surface 

 (tii. ^- c.. ti^-. 1T>. b.). to ^hieh two animalcules arc 

 ah\a> N adhering:. 



In the IHtittunctit' . for e\. in the Diatomu 

 Stratum (PI. l\ . li^. :>S.). the cuira>s i< flattened on 

 the ediv>. and cut iu half eireles, \\hilst, \\here tlu* 

 animalcules are adheriiii' , it forms a narron sin 

 of reunion (fig. 38. b.). The form of this surface 

 eon e^poiids a! \\a\s with that of the eniras> , \\- it 



* 



