EOLIS. 



a small cluster of roundish, yellow, irregular follicles, and frequently a smaller gland of two 

 or three follicles is placed a little in advance. They are connected by a long slender duct, 

 which opens into the mouth at the commencement of the oesophagus. 



The oesophagus is short, with a longitudinally plicated mucous membrane, and is usually 

 bent into the form of an S, allowing the mouth to be advanced with great facility. The 

 stomach is a large pyriform pouch, which lies diagonally in the body (Figs. 1 c, 2 d, 3 d,4 d), the 

 lower end approaching to the left side : it is continued in the form of a canal, in some species 

 wide and tapering, in others more constricted, down the median line of the back, and termi- 

 nates near the posterior extremity of the body in a blind sac. From the pouch and its 

 continuation, branches are given off in pairs, not quite symmetrical, but generally more or 

 less alternating. These branches, after being redivided in most of the species, give off smaller 

 tubes, which are continued into the branchial papillae. From the upper surface of the posterior 

 extremity of the stomach, where it is continued into the central canal, is given off a short 

 intestine, which passes to the right side, opening in a small nipple-like anus, generally 

 concealed among the branchiae. The inner walls of the stomach are longitudinally plicated 

 (fig. 13) ; the plications being usually continued more or less extensively through the branches. 

 The arrangement of the lateral branches in this curious digestive apparatus varies in different 

 sections of the genus, as given in the accompanying plates. In the first section, represented 

 by K papillosa (fig. 2), the branches bifurcate once, or sometimes twice, before they reach 

 the extremities : in the second section, represented by R coronata (fig. 4), the lateral branches 

 have a pectinated arrangement ; the more simple forms of the third and fourth sections are 

 shown in U. olivacea (fig. 3), and K despecta (PL viii, fig. 8). 



The prolongations of the branches that enter into the papillae, there undergo a con- 

 siderable enlargement and change of form, and from the variety and brilliancy of their 

 colouring, are the chief attraction of these elegant little animals. The simplest form of this 

 peculiar organ is met with in U. concinna, where it is a mere dilated tube, having its walls 

 slightly waved, and the inner surface sprinkled with darkish granules. In U. Farrani 

 (PI. 8, fig. 10) it still retains a considerable simplicity of structure, but becomes decidedly 

 sacculated. The complexity is much increased in U. olivacea, in which it is produced into 

 puckered follicles or sacculi. But in F. papillosa (fig. 9) it appears to attain its highest 

 development. The central canal is there somewhat tortuous, and gives off on all sides 

 variousty-sized irregular blind sacs, which are crowded with little compound follicles. The 

 whole of the inner surface is lined with a thickish layer of irregular vesicles or globules, filled 

 with numerous granules. These last, when submitted to a high magnifying power, are seen 

 to be of various sizes, transparent, rounded and nucleated. The whole of the internal 

 surface of the gland is covered with vibratile cilia. These compound glands are evidently 

 biliary organs, diffused throughout the several papillae, and supplying the place of a compact 

 liver, which is wanting in the body of these animals. The stomach and biliary organs are so 

 intimately connected in this genus, that it is not easy to point out the limits of each ; they 

 appear to differ in different species. In E. papillosa the central canal is evidently a 

 continuation of the stomach, and the plicated internal membrane is not only continuous 

 throughout it, but also passes into the lateral branches, which thus appear to form a part of 

 the same organ. On the other hand, we find in some species coloured granules, similar to 

 those of the papillae, partially lining the ramifications, as in E. gracilis, E. rufibranchialis, 



