328 EVENINGS AT THE MICROSCOPE 



up the severed and shrunken sucker, and lay it in a little 

 sea- water in the live-box. 



Under a power of 180 diameters we see that the tube 

 is composed of two series of muscular fibres, the one set 

 running lengthwise, the other transversely or annularly; 

 the former by their contraction diminishing the length of 

 the tube, the latter diminishing its calibre. The muscular 

 walls are covered with a transparent skin, studded with 

 round orange-colored spots, perhaps glandular, exactly 

 similar to those we saw on the exterior of the spines and 

 Pedicellaria. 



Now, to illustrate the action of these tubular feet, I 

 must again have recourse to the denuded shell of a pre- 

 served Echinus. Taking this globose empty box into your 

 hand, hold it up against the light, looking in at the large 

 orifice, which was once occupied by the mouth; you see 

 that the whole shell is pierced with minute holes pores, 

 which are arranged in ten longitudinal, or meridional lines, 

 associated so as to make five pairs of lines. Now, with 

 a lens, scrutinize more minutely a portion of any one of 

 these lines, and you discern that it is composed of a mul- 

 titude of pores, which have a peculiar order of arrange- 

 ment among themselves; that is to say, they form minor 

 rows which cross, obliquely or diagonally, the course of 

 the meridional line. These rows -are themselves double, 

 the pores running in pairs, not, however, with mathemat- 

 ical symmetry. In this species there are three pairs of 

 pores in each row, and so there are in the one which I 

 have here alive, but in other of our native species the 

 rows consist of five pairs. 



These pores are intimately connected with the tubular 

 feet, each of which springs from a portion of the shell that 



