64 PRACTICAL HISTOLOGY. 



separate the bars one from another by means of 

 needles ; the preparation may then be covered and 

 observed. 



Valve of mnesel. showing br, br, the expanded gills or branchiae, which 

 owing to the little bars of which they are composed, present a striated 

 aspect. 



ml, mantle ; m, cut adductor moscle ; i, mass of viscera ; the dark pro- 

 jection just above is the foot. 



Each of the bars in question will be seen to be 

 fringed with large cilia, which are set at an appre- 

 ciable distance apart along nearly its whole length, 

 but at the free extremity of the bar are much more 

 densely arranged. Those in this situation resemble 

 in appearance the cilia of the frog's mouth, with the 

 exception that they are very much longer ; and like 

 them they appear to spring a large number from 

 each cell, whereas the others are stiff-looking and 

 obviously thicker, and are connected at their base 

 each to a single, comparatively small epithelium 

 cell. In spite of these differences of appearance and 

 attachment the two kinds seem to be essentially 

 alike in nature, for the mode in which they move 

 is similar, and they are similarly affected by re- 

 agents. 



It will be found that after a preparation such as 

 that just described has been made for several hours 



