OF TUBULAR AND CELLULAR POLYPI, AND OF ASCIDI^. 371 



Cavolini saw the currents in all the Sertularice observed by him, but he did not 

 detect their continuation into the stomach of the expanded polypi ; a circumstance 

 equally belonging to every species that I have met with. Had he done so, he must, 

 it would seem, either have included the stomachs, with the branches and the root, 

 under the name of heart, or probably would have relinquished a term which, on 

 several accounts, appears to be misapplied. His not having perceived the stream of 

 communication may be accounted for by its being generally much smaller and less 

 conspicuous in a short space near the base of the cells, as well as less regular in its 

 periods, than that which runs along the stems and footstalks. 



Sertularia pumila, Plate VIII. fig. 3. (Ellis, pi. v. a, A.), was gathered growing above 

 low water mark at Dover, October 1832. Each of its cells is divided near its base 

 by a partition a, on which the polypus is fixed, and which may be seen to be pierced 

 with an oval hole 6, if a section of the shell is made a little above or below it. In 

 the complicated cell of S. pluma, last described, this perforated septum was not de- 

 tected ; but I believe it to exist throughout the family. Sertularia ahietina has the 

 aperture long and narrow. In Campanularia it seems to be round, and in the middle 

 of the septum, which in that genus is very conspicuous. 



The connexion between the stomach and the stem, by the aperture, takes an angu- 

 lar course in the present species, and could not always be perceived. One polypus 

 had within its mouth revolution of darkish substances, which after a while it dis- 

 gorged ; in the stomach of the same there was irregular motion of particles, and an 

 action seemed to be going on between the two ; the upper part of the neck some- 

 times swelling, and the cavity of the mouth extending down that portion in a tubular 

 form. Within other expanded polypi, no motion could be detected. 



In the substance of the necks of the polypi, transverse lines were visible, bearing 

 a resemblance to those characteristic of voluntary muscle in the higher animals. 

 I have observed the same appearance on a band forming the edge of the bag of 

 a Lucernarla, and also very distinctly in the axis of its numerous knobbed ten- 

 tacula. 



Sertularia setacea, Plate VIII. fig. 4. (Ellis, pi. xxxviii. 4 D. Plumularia setacea, La- 

 marck,), was found at Brighton on flag, with which the shore was strewn after a 

 storm, July 1833. It was distinguished by its subcorneal cell, so short as commonly 

 to shelter only a part of the stomach, and by its spinous ovaries, differing from those 

 in Ellis's figure, and mostly sessile on the creeping root. The ova within were 

 opake and yellow. Its polypi had from sixteen to nineteen arms, and when they were 

 full-blown it was an object of remarkable beauty. From its transparency, and the 

 smaller number of its moving particles, their individual quivering motions and the 

 course of its currents were more conspicuous than in the former two species. The 

 stream sometimes extended only to the pulp below the septum, and sometimes 

 mounted into the stomach; and in whichever part it terminated, agitation took 

 place there on the ceasing of the upward flow. The soft part within the branches. 



