OF TUBULAR AND CELLULAR POLYPI, AND OF ASCIDIJE. 383 



casionally contracted forcibly to reject what had been stopped by the tentacula, or 

 found unfit for food. The oral opening, instead of projecting-, was then drawn down 

 below the level of the coat, and depressed it; the ciliie being also at such times closely 

 stretched across the openings of the spiracles {d). Whenever the ciliae stopped their 

 action, they were seen to be very numerous and appeared almost as a continuous 

 membrane. 



The conveyance of the food from the different parts of the mouth to the stomach 

 by an even progress, and without any muscular act of swallowing, remained as my- 

 sterious as before. 



No note was taken of the existence of alternations in the circulation of this poly- 

 clinum ; and I cannot now assert it as a fact, though I believe it to be so. It would 

 be interesting to trace the limits of that phenomenon in the animal kingdom *. 



No indication of a nervous system was noticed in either of these Ascidice\ and not 

 being previously prepared for the investigation by reading the labours of others, it 

 did not occur to me to look for it. 



CELLULAR POLYPL 



It may assist towards establishing the place of Cellularia and Flustra to add some 

 general remarks on such species of those genera as came under my observation. 

 These all appeared to belong to one natural family, far higher in its organization 

 than the tubular polypi, with which some of its members are even yet associated. 

 They show nothing of the internal currents which in the Sertularice connect the dif- 

 ferent parts of the zoophyte ; nor indeed have I succeeded in any instance in detecting 

 their circulation. Each animal when retracted is inclosed entirely by its cell ; through 

 a valve in which, the arms and mouth are sent out. A short sheath mostly pre- 

 cedes them, from whence the arms rise straight together, and then open to a funnel- 

 or bell-shaped figure of beautiful regularity. Though radiating like those of the 

 Sertularice, they are organs of a different kind ; not extended motionless, waiting for 

 such food as may be drifted to them, nor rough with irregular projections for at- 

 taching it, but uniformly fringed with a row of cilise on each side ; of which the 

 lively action is so identical with that on the spiracles of the Ascidice described, that 

 I cannot doubt them to serve, "equally with those, the double purpose of drawing 

 food to the mouth by currents, in the water, and of respiration. In all cases which 



* Since the reading of this Paper, an extract from one of the letters of Kuhl and Van Hasselt has been 

 pointed out to me in the Bulletin des Sciences Naturelles, tom. ii. p. 212, which is dated in Java 1821, and 

 announces their discovery of the same kind of circulation in the Biphorce. Cuvier in his Rfegne Animal, 

 edit. 1830, does not notice this; and in 1824 Blainville, in the 32nd volume of the Dictionnaire des Sciences 

 Naturelles, p. 114, only refers to the account as being not understood. 



• It ought also to be stated, that in the 60th volume of that work, pubUshed 1830, article ' Zoophytes,' the 

 currents in the medullary part of the Sertularice are mentioned as characterizing that family, and are considered 

 to be an oscillation analogous to what is seen in some plants. In the same article the arms of their polypi are 

 described as ciliated. 



3 D 2 



