EOLIS. 



E. Northumbrica, and others ; while in U. despecta the central canal, all the ramifications, 

 and the glands of the papillae are coloured and granulated alike, implying a greater diffusion 

 of the biliary function. 



The food, after being partially digested in the stomachal pouch, is driven in detached 

 portions through the alimentary system by the alternate contractions of the pouch and great 

 trunks leading from it ; these contractions are only of a nature to produce an oscillatory 

 motion, which serves to promote that intimate mixture of the alimentary matters with the 

 hepatic and other secretions, necessary to the process of digestion. 



A curious organ, apparently in connexion with the digestive system, but whose func- 

 tions are very imperfectly understood, is situated at the end of each papilla. It is a 

 small ovate vesicle, which communicates with the biliary gland by means of a slender canal 

 below, and at the opposite and narrower end opens externally through a minute aperture at 

 the extreme apex of the papilla. (PL 8, figs. 9 a, 10 a, 1 1 a.) The walls of this vesicle, which 

 are seen of an opake white in the species with a transparent skin, consist of a strong thick 

 layer of finely interwoven circular muscular fibres. The contents appear to be arranged in 

 longitudinal masses. When very highly magnified these masses are found to contain long, 

 narrow, elliptical bodies, with faint double longitudinal markings, (fig. 14 a,) and globules of 

 various sizes, containing either one nucleus or several small granules in their interior. These 

 are imbedded in, and adhere to, a tenacious, obscurely granular mucus-like matter. We have 

 frequently seen the elliptical bodies violently ejected from the terminal orifice ; they are then 

 observed to be contained in little transparent membranous bags, each holding half a dozen 

 or more. (PI. 8, fig. 12.) In some species these bags likewise contain other and larger flat- 

 tened elliptical bodies, with a peculiar marking in the interior. (Figs. 13, 16.) Immediately 

 after expulsion the membranous bags burst, and the contained narrow elliptical bodies becoming 

 scattered, each shoots forth from the end first protruded, a much prolonged, slender, hair-like 

 filament. (Fig. 14.) On one occasion we observed an individual of E. picta, when moving 

 freely about, suddenly, and by a convulsive effort, eject from the points of the papillae a 

 minute stream of milk-white fluid, which curling upwards, mingled with the surrounding liquid 

 and was soon lost to view. The fluid exactly resembled the contents of the ovate vesicle when 

 forced out by pressure, and examined with a lens of low power. It appears probable that 

 this extraordinary apparatus at the end of each papilla is an organ of defence ; and from the 

 resemblance of the minute bodies ejected to those stated to be thrown out by the Actinia, that 

 they are stinging bodies of a similar nature. 



The vascular system appears to be as complete as in any of the order. The heart is 

 situated immediately below the skin, near the centre of the back, where it forms externally 

 an oval swelling ; it is composed of two parts, a ventricle (PL 8, fig. 1 a) and an auricle 

 (fig. 1 b) ; these are inclosed in a very delicate pericardium of an elliptical form. The 

 ventricle lies in front of the auricle, and the communication between them is effected by 

 a small orifice on the under side. The ventricle is strong and muscular, and has in the 

 interior numerous fleshy anastomosing columns. When examined after death it is some- 

 what pyriform, with the narrow end anterior, and having the aorta issuing from it. 

 This vessel (fig. I d) is of considerable size, and branches may be traced from it to most of 

 the principal organs. The auricle is much more delicate than the ventricle, and, like it, is 

 provided with fleshy columns in the interior, only they are much finer and less numerous. 



