Pt Des 
REPORT ON THE CRINOIDEA. 89 
left. When it has reached the bottom of the visceral mass the intestine turns off to 
the right, and coils round its anterior side. It follows the watch-hand, until it has 
reached the hinder part of the disk, behind the commencement of the first coil (fig. 2). 
Here it turns upwards and slightly forwards, to end in the anal tube. The spiral form of 
the whole organ is thus almost identical with that of the so-called digestive organ in 
the Palzocrinoids, which I believe to be nothing but the more or less calcified connective 
tissue that supported the intestinal wall, as explained in the previous chapter. 
In simple forms, like Rhizocrinus and Bathycrinus, more especially the former, the 
development of the gut is but slightly more advanced than it is in the Pentacrinoid. 
Horizontal sections through the lowest part of the cup of the larva are remarkably 
similar to corresponding sections of Rhizocrinus and Bathycrinus, such as are represented 
in Pl. VIIb. figs. 6, 7, and Pl. VIIIa. fig. 8. 
Fic. 2.—Diagram showing the course of the Digestive Tube in an endocyclic Crinoid (Antedon, Pentacrinus, &c.), 
as seen from the ventral side. 
A, B, C, D, E, the five ambulacra of the disk ; m, mouth ; @, anus. 
The lower part of the cup between the second radials is occupied in Bathycrinus 
and in the Pentacrinoid larva by a large expansion of the lowest portion of the coiled 
gut, just as described in Rhizocrinus by Ludwig.’ It is somewhat kidney-shaped in 
section, and the concavity is occupied by the plexiform gland, which is always inter- 
radial in position where it comes out of the calyx (Pl. VIIb. fig. 6, x). 
At the level of the third radials of Bathycrinus, or the second brachials of Rhizocrinus, 
the circular course of the intestine is more apparent, and the plexiform gland is separated 
from the body-wall by the rectum, as shown in PI. VIIb. fig. 7, and Pl. VIIla. fig. 8. 
In both of these figures the « indicates the plexiform gland, which is here situated just 
below (¢.e., south of) the lower end of the fore-gut, where it passes into the mid-gut or 
intestine generally. 
' Zur Anatomie des Rhizocrinus lofotensis, M. Sars, Zeitschr. f. wiss. Zool., 1877, Bd. xxix. p. 64. 
(ZOOL. CHALL. EXP.—PART XXx11.—1884.) Ti 12 
