KEPORT ON THE ClUNOIDEA. 89 



left. "When it has reached the bottom of the visceral mass the intestine turns off to 

 the ridit, and coils round its anterior side. It follows the watch-hand, until it has 

 reached the hinder part of the disk, beliind 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 Palajocrinoids, 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 Rhizocrimis 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 remarkal)l3- 

 similar to corresponding sections of Rhizocrinus and Bathycrimis, such as are represented 

 in PI. Vllb. figs. 6, 7, and PI. Villa, fig. 8. 



W 



E 



Fig. 2.— Diagram showing the course of the Digestive Tube in an endocyclic Crinoiil (Antedon, I'entacrimui, &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 Batkyerinns 

 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 Vllb. 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. Vllb. fig. 7, and PI. Villa, fig. 8. 

 In both of these figures the x indicates the plexiform gland, which is here situated just 

 below {i.e., south of) the lower end of the fore-gut, where it passes into tlie mid-gut or 

 intestine generally. 



1 Zitr Anatoiiiie dcs Rliizocrinu.s lofoteii.si.'*, M. Sar?, Zdhchr. f. wiss. Zool, 1877, Bd. xxix. p. 64. 



(ZOOL. CHALL. EXP. — PART XXXIT. — 1884.) li 1'- 



