124 
ME. II.. N. MOSELEY ON THE 
notwithstanding the actual continuity of the muscle with the mesentery 
above, in order to show the position of the ovum (O). At the bottom of 
the atrium, i. e. the central canal leading from the mouth and tentacles to 
the exterior, and formed by the deep retraction of the animal, are shown 
the mouths of the tubes formed by the introversion of two tentacles as 
they appear when looked directly into. 
On the right-hand side of the figure three tubular cavities (TC, TC, TC), 
forming the so-called ccenenchym, are represented, lined by their soft tissues, 
composed of the same three layers as compose the lining of the calicle. 
Two of the tubes communicate above, over their lateral wall, by one of the 
deep canals. On the left-hand side of the figure portions of the plates of 
hard tissue forming the lateral walls of the tubular cavities are shown (A, A), 
with their natural upper margin. Two systems of canals are seen in sec- 
tion near the surface of the coral. The most superficial canals (V, V, V) 
lie almost immediately beneath the external epithelial layer ; they are more 
numerous and much smaller than the deeper canals (V', V'), which form com- 
munications between the adjacent tubular cavities passing over the summits 
of the lower parts of their walls, as is seen on the right-hand side of the 
figure. Both sets of canals are lined with entodermic cells. 
A A. Portions of the walls of the tubular cavities. 
CT. Calcareous tabulae. 
P. Projecting points of calcareous tissue. 
E. Epithelial layer of ectoderm. 
EN. Entodern. 
C. Layer of homogeneous connective-tissue. 
D. Layer of connective-tissue cells. 
T. Tentacles introverted, seen in longitudinal section. 
T'. Tentacles introverted, viewed directly into their mouths. 
S. Cavity of stomach. 
EM. Be tractor muscle. 
MF. Mesenterial filament. 
TC. Tubular cavities of coenenchym. 
V. Superficial smaller vascular canals. 
V'. Deep larger vascular canals. 
Fig. 2. Section vertical to the upper surface of Sarcophyton , sp., showing three sexual 
polyps and a number of zooids. 
The polyps are represented in the contracted condition ; they occupy 
three large elongate cavities in the general transparent sarcosome. The 
tentacles here are not introverted simply but retracted. The sarcosome 
between the polyp-cavities is traversed by an elaborate network of canals 
belonging to two systems, a transverse one, and a vertical one, which, how- 
