288 EVENINGS AT THE MICROSCOPE 



behind the rotatory organ ; for though I have not traced it 

 when empty, I have seen the fecal matter driven rapidly 

 upward as through a canal, until the mass was discharged 

 just behind the sinuous cleft. On our mixing carmine 

 with the water the effect is very striking; the particles, 

 whirled round in two circular vortices, are poured in an 

 accumulated torrent through the sinuosity, and over the 

 elevation at the front of the head. We presently perceive 

 a slender line of crimson passing down below the mastax, 

 which indicates a slender stomach tube there; and, after 

 a while, a little ball of the same pigment accumulates and 



WHEELS OF TUBE-WHEEL. 



is seen resting a little lower down. This then indicates 

 the form and position of the stomach; it must be a very 

 slender canal, terminating in a small rounded bag, at about 

 one- third of the distance from the mastax to the base of 

 the tube. The lengthened sac which you see is the ovary, 

 from which the eggs are discharged into the lower part of 

 the case. 



The mouth needs a little explanation in detail. As 

 you see it, you probably discern little resemblance in its 

 parts to the same organ in Brachiomts, and yet essentially 

 it is formed of the very same constituents; and as it is 

 very instructive to observe the modifications, in different 

 animals, of a common model of any particular organ, it 



