34 
delicate membranes, leaving the lacunae exceedingly spacious. The 
transverse muscles (figs. 23 and 24, tf) slanting inwards and down- 
wards and more circumstantially described above, take their course 
partly between these laminae. Of the stronger bundles there occurs 
one on about every three or four laminae. Their course and the 
partial support they afford to the walls of the intestine can be very 
well studied by direct preparation. 
The chänge from the intestine to the rectum is much more grad- 
ual than that from the same to the pharynx. It is a gradual 
narrowing of the lumen, and at the same time the ventral floor of 
the intestine is inclined upwards, the rectum winding its way through 
the complex mass of the genital apparatus, passing under the pe- 
ricardium (P, fig. 46) enclosed between the ducts dd’ and ARA’R' 
and finally lying above the median terminal portion Q of all these 
ducts. Just about here the lumen is the smallest, it then com- 
municates with the anal cavity which momentarily widens out again 
and leads to the exterior by the opening A (fig. 13). 
As to the walls of the rectum they are (as are those of the 
anal cavity) all over covered with very long and numerous cilia, 
no longer restrieted to a dorsal and ventral intestinal furrow. The 
rectum is peculiarly folded (fig. 32, Rec) and in the wide longitudinal 
spaces exteriorly enclosed between these folds, the accumulation of 
blood-corpuseles is very considerable (vide infra). Here too the walls 
are merely of one cell-layer in thickness, sustained by a very delic- 
ate membrane. The cells of this beautifully ciliated epithelium are 
provided with very distinct nuclei. 
Posteriorly along a very short tract muscülar fibres are develo- 
ped in connection with its walls, which in one place become thickly 
set and numerous enough to form a sort of sphincter (fig. 34, spm). 
This is in the immediate vicinity of the opening of the reetum into 
the anal cavity. In this cavity I find in my longitudinal sections 
a clot of feces about to be expelled. Numerous diatoms are con- - 
tained in it, which may be regarded as the animal’s natural food, 
rather than the coral above mentioned. 
