332 



EVENINGS AT THE MICKOSCOPE. 



SUCKER OF cr.cniN. 



has suddenly slirunk up to a sixth part of its former 

 lengtli, exchanging at the same time ifs smooth slender- 



iiess and transhicencj for 

 a conjugated semi-opa- 

 city. I push the knob 

 aside with a needle's 

 point and thus destroy 

 its adhesion ; which done, 

 I take np the severed and 

 shrnnken 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 length- 

 wise, the other transversel}^ or annularly ; the former 

 by their contraction diminishing the length of the tube, 

 the latter diminishinc: its calibre. The muscular walls 

 are covered with a transparent skin, studded with round 

 orange coloured s])0ts, perhaps glandular, exactly simi- 

 lar to those we saw on the ex- 

 tei'ior of the spines and Pedlcel- 

 lar'ia. 



Now, to illustrate the action 

 of these tubular feet, I must 

 again have recourse to the de- 

 nuded shell of a preserved 

 Echinus. Taking this globose 

 empty box into your hand, hold 

 it up against the liglit, looking 

 in at the large orifice, which 

 was once occupied by the mouth ; — you see that the 

 whole shell is pierced with minute lioles — pores, which 



PORES OF URCHIN. 



