REPORT ON THE PENNATULIDA. 193 



EEPORT ON THE PENNATULIDA 



COLLECTED IN THE OBAN DREDGING EXCURSION 



OF THE BIRMINGHAM NATURAL HISTORY AND 



MICROSCOPICAL SOCIETY, JULY, 1881. 



BY A. MILNES MARSHALL, M.A., D.SC, PROFESSOR OF ZOOLOGY 

 IN OWENS COLLEGE, AND W. P. MARSHALL, M.I.C.E. 



(Continued from page 151.) 



Pennatula Phosphokea (continued). 



f. The Mesenterial Filaments. — The mesenterial filaments, which 

 are simply the thickened edges of the mesenteries below the stomach, 

 fall, as already noticed, into two sjroups : a set of two situated on the 

 upper surface of the leaf and extending down to the bottom of the 

 polype cavities, the lomi mesenterial filaments, Figs. 4 and 5 s ; and a set 

 of six, the short mesenterial filaments, Figs. 4 and 5 r, which only 

 extend a short way below the stomach. 



The long mesenterial filaments have the same character along the 

 whole of their length. They are straight, or very slightly convoluted, 

 and are in transverse section (Fig. 5 s) bifid, the filament and 

 mesentery together having the appearance of a letter Y with very 

 thick arms. Each arm consists of a thizi stratum of connective tissue, 

 clothed on its upper surface — that towards the upper surface of the 

 leaf — by a thin layer of flat epithelial cells, and on its under surface by 

 a single layer of elongated columnar ciliated cells, which are granular 

 in appearance, and possibly in part of glandular nature. Concerning 

 the function of these long mesenterial filaments we know nothing. 



The short mesenterial filaments, Figs. 4 and 5 r, are like those of 

 Funiculina thick and much convoluted. They are rather shorter than 

 those of Funiculina, being not quite so long as the stomach in its ex- 

 panded condition, and their length is the same in all the polypes of 

 the leaf, however long or short these themselves may be. They com- 

 mence about the spot where the polypes become free from one another, 

 so that the greater part or whole of their length is contained in the 

 leaf proper. 



The structure of the short mesenterial filaments is, as shown in Figs. 

 4 and 5, the same as in Funiculina, each consisting of a connective 

 tissue lamella clothed on each side by a thick layer of special glandular 

 and ciliated endodermal cells. Concerning the function of these 

 filaments we have been able to make some observations which tend to 

 strongly confirm Dr. Krukenberg's conclusions* that they are really 

 digestive organs. 



In a number of the polypes we have observed solid bodies imbedded 

 either partially or completely in the mesenterial filaments ; examples of 

 this are shown in the third section in Fig. o, f o. These bodies are 

 clearly of a foreign nature ; they are also evidently organised, and 

 appear to be undergoing decomposition. From the observations of Dr. 

 ■*■ Vide supra, p. 34. 



