1898-99. } THE MESENTERIAL FILAMENTS IN ZOANTHUS SOCIATUS. 391 
Three years later I described (1889) the two portions of the filaments 
of Zoanthus flos-marinus, and, in addition, noted that the cells covering 
the surfaces of the mesenteries for some distance outwards from the 
glandular portions of the filaments were much higher than the general 
endoderm, and were loaded with green granules and fragments of sponge 
spicules. I suggested that this region of the endoderm was essentially 
digestive in function, an opinion which has since been confirmed experi- 
mentally by Willem (1893) for the Hexactiniz. 
Haddon and Shackleton (1891 and 189!a@) confirmed my observations 
in other Zoanthids, and pointed out that slight variations in the form of 
the ciliated lobes occurred in certain forms, such as P. axinelle. Finally, 
Von Heider (1895), in his description of Zoanthus chierchie@, entered 
somewhat fully into the structure of its mesenterial filaments. He 
found in the ciliated bands what he regarded as a distinct area inter- 
vening between the central lobe and the ciliated portions of the lateral 
wings, and characterized by possessing numerous gland cells. He terms 
it the glandular swelling, and attributes to it a digestive function. He 
also observed the heightened epithelium lateral to the glandular portions 
of the filaments, which had been described by Haddon and Shackleton 
and myself, but objects to its interpretation as a digestive area, believing 
it to be the region in which the reproductive cells are to develop, none 
of the specimens which he examined possessing these cells. 
I].— DESCRIPTIVE. 
I. The Ciliated Bands. 
To correctly inter- 
pret a series of trans- 
verse sections of an 
adult Zoeanthus, it is WH) yy UY yj yj 
necessary to under- WY; 1 Win. 
stand the course of ~ Yy Y Yj STs 
the free edge of the YY 
mesentery. For this 
purpose I made a wax 
reconstruction of the 
upper part of one of Fic. 1.—Diagram to show the relations of the ciliated bands. St= 
Stomatodzum ; 4A, BR=level of sections shown in Fig, 2: CC=level 
the perfect mesen- 
of Fig. DD=level of Fig. 4. 
teries of Zoanthus 
soctatus, together with the portion of the stomatodeum to which the 
mesentery was attached. From this it is evident that the lower edge of 
