396 TRANSACTIONS. OF THE CANADIAN INSTITUTE. ~ [Vou. VI. 
thickening in Z. Wacgillivrayi and von Heider in Z. Chterchie, the \at- 
ter however taking exception to my interpretation of its function, and 
believing it to be the area in which the reproductive elements will devel- 
op. This idea is readily disproved by the examination of specimens 
in which the gonads are developed. For instance, I have preparations 
of Z. nympheus which show the thickened endoderm very distinctly, 
crowded with foreign bodies, and quite externally to this, in the region 
where the endoderm has assumed its usual low form, the sexual cells 
are found. On the other hand, my interpretation is confirmed by Willem 
(1895), for it is in exactly the region of the thickening that he finds an 
abundant ingestion of carmine particles in the Hexactiniz, these forms 
also presenting thickenings of the endoderm, usually less pronounced 
than in the Zoanthids, immediately external to the glandular streaks of 
the mesenterial filaments. 
It is very generally believed that the epithelium of the middle lobe of 
the ciliated bands is in direct continuity with the epithelium of the 
glandular streak ; indeed it has generally been regarded as the upper 
part of the glandular streak. It appeared that there was a marked dif- 
ference in Z. soctatus between this median epithelium and that of the 
glandular streak and to test the accuracy of this appearance I endea- 
voured to obtain a longitudinal section of the 
filament which would cut the epithelium of the 
median lobe above and the glandular streak 
below. After many trials I obtained a series 
from three successive sections of which it was 
easy to reconstruct a median section through 
the filament. Such a reconstruction is repre- 
sented in Fig. 5, somewhat diagrammatically. 
In Fig. 6 is shown the appearance ofa portion 
of the stomatodzal 
ectoderm for the re- 
gion indicated in 
Fig.5 by a. It will 
be seen from this 
that the epithelium 
in thisregion is high 
Fic. 5.—Reconstruction from three - 5 . 
sections of 4 longitudinal, section) SanGetnat IuGONtalns 
through the stomatodzeum, the numerous g ] an d ; 
median lobe of a ciliated band and a 3 f : 
glandular streak of Z. soctatus ; a-d cells with clear con- Fic. 6.—Portion of Fig. 5 about 
3 2 i highl 
=the levels: from which Figs. 6-9 are the region marked a, more highly 
taken. — tents; gland cells magnified. 
