DESM1DIAC. 



285 



proposed by Mr. Rainey, and adapted to a l-4th achro- 

 matic condenser ; with which must be used a l-8th ob- 

 ject-glass. The Gillett's condenser, or parabolic reflector, 

 will do equally well it used with a 1-Sth objective. In 

 diagram A, tig. 156, a specimen of the 0. Lunula, as seen 



Fig. 156. Clotteria Lunula. 



with the above arrangement of microscopic power, and a 

 deep eye-piece, the cilia are in full action along the edge of 

 the membrane which encloses the endochrome ; and also, 

 but not so distinctly, along the inside of the edges of the 

 frond itself. Their action is precisely the same as that 

 in the branchiae of the mussel : there is the same wavy 

 motion; and as the water dries up between the glasses 

 in which the specimen is enclosed, the circulation becomes 

 fainter, and the cilia are seen with more distinctness. 



In diagram A, a line is drawn at 6 to a small oval mark; 

 these exist at intervals, and more or less in number over 

 the surface of the endochrome itself, beneath the mem- 

 brane which invests it. These seem to be attached by 

 email pedicles, and are usually seen in motion on the spot 

 to which they are thus fastened ; from time to time they 



