OF TUBULAR AND CELLULAR POLYPI, AND OF ASCIDI^. 367 



tions of smaller ones ; a few were nearly globular, but in general they were of no 

 regular form. The tube had between the lines of more conspicuous spots a granu- 

 lated appearance, and beneath this the currents ran ; but I could not, by altering the 

 focus of the microscope, detect the opposite current on the further side, as may be 

 done in Chara, owing to the interposition, in most parts, of a grumous matter. Some 

 of the larger particles of this were like those in circulation, and by close attention 

 might be seen slowly to change their relative positions. 



At the nodous parts c d e were slight vortices in the current : at c near the end of 

 the tube it came over from the opposite side, and I could not at this time succeed 

 in detecting the passage of any particles between the tube and the stomach of the 

 polypus. 



Between the stomach b, and the mouth a, a remarkable action went on, wholly 

 different from that in the tube. The mouth became swollen by a flow into it from 

 the stomach, to the shape shown at « 3 : this flow continued for about a minute. The 

 contents of the mouth were then squeezed back into the stomach, which expanded 

 as the mouth contracted {a b). During this reflux the connecting orifice was seen 

 distinctly open, and it continued so on the return of the flow to the mouth {a 2), till 

 the stomach became nearly emptied. The orifice then closed gradually, preparatory 

 to the effort of forcing the fluid back to the stomach. The intervals between that 

 act were very evenly eighty seconds. 



Two currents were continually going on, both in the mouth and stomach, one 

 flowing always down the sides in the direction a b, and an opposite one in the axis ; 

 except that the latter was suspended at the time of the close contraction of the 

 stomach and of the discharge from the mouth into it. 



The creature was observed at intervals throughout the day from ten in the morn- 

 ing ; its appearance continuing much the same. The front arms sometimes spread 

 themselves a little, and at one time a cloud of particles hung before them in the 

 water like those within the mouth, and which seemed to have been recently ejected. 

 Though the swelling and contracting continued, no motion was seen in the ejected par- 

 ticles ; proving that in the ordinary course of this action the mouth was not opened. 



The next morning the polypus was found much altered (a 4) ; the hinder arms, or 

 those of the neck, were shrunk to an indistinct mass, appearing to be partly ab- 

 sorbed and partly thrown off^, and a stream of particles was drifting away from them. 

 The least imperfect of these arms had a rapid action going on in its granular sub- 

 stance, which ended in a current within it towards its root. The terminating arms 

 appeared as perfect as the day before. 



Rudiments of the horny shell had extended to the neck from/, its end when it 

 was first observed. The currents in the intermediate space b were now plainly 

 connected with those in the tube and had lost their former even course, the particles 

 flowing about irregularly as the division between h and c became by degrees broken 

 away. The currents in the tube were unaltered. 



3 B 2 



