108 ANATOMY OF THE ANOPLA. 



which often occur so abundantly in these worms. When the animal, after spawning, has 

 regained condition in its native haunts, the granular cells of the digestive chamber become 

 largely developed, so that in transverse section the body is rounded (Plate XX, fig. 3), and the 

 entire middle region filled up by the mass, with the exception of an irregular fissure in the 

 centre ; whereas considerable atrophy of these elements occurs during long confinement, or the 

 exigencies of reproduction. Towards the posterior end of the worm the tract is much diminished, 

 and, in the living animal, more evidently ciliated when viewed from above. The minute structure 

 of the wall of the cavity (Plate XVIII, fig. 16) bears much resemblance under pressure to 

 that of the ciliated oesophageal region in Jmpkiporus, having a basement-substance, in which are 

 imbedded a vast array of granular glands, and with the inner surface richly ciliated. The 

 contents of the glands (Plate XXI, fig. 7) consist of granular cells and globules, which readily 

 escape from the free border of the organ, and are often ejected per anum. 



In Carinella and Valencinia this and the previous region agree so closely with the 

 arrangement in Linens that no special description is necessary. 



The ciliation of the entire digestive canal is more apparent in Ceplialotlirix linearis than in 

 Linens. It has a similar arrangement in transverse section (Plate XXI, fig. 2), and the same 

 gregariniform parasites and an Opalina occur. In structure the first or oesophageal portion has a 

 much more lax and cellular aspect than the succeeding densely granular region ; and from the 

 translucency of the animal the distinctions between the divisions are more exaggerated. In one 

 specimen sent from St. Andrews in April, the digestive chamber was coloured of a fine pea-green 

 (Plate IV, fig. 5), instead of the usual pale pinkish hue, a state due to the uniform tinting of the 

 cellular elements, it may be from the nature of the food, such as the deep-green ova of Phyllodoce. 



Ehrenberg, De Quatrefages, Girard, and Stimpson considered the mouth to be the genital 

 orifice, the former observing that a large quantity of mucus was discharged therefrom. Mr. H. 

 Goodsir thought the canal common to the respiratory, digestive, and generative systems. " In 

 Serpentaria" he observes, " it acts almost as an organ of digestion, while in Nemertes there is a 

 trumpet-shaped exsertile proboscis, which, contrary to the opinion of Rathke and other 

 naturalists, and according to the opinion already expressed by Ehrenberg, is the intestinal 

 canal." He agreed with Ehrenberg in supposing the ova escaped into this chamber. His 

 views were rather erroneous, such as imagining the first region of these worms to be composed of 

 a single annulus ; but the succeeding or terminal of many, each about an -Jth of an inch in length ; 

 moreover, that each of the separate annuli contained all the elements of the perfect or original 

 animal, viz., a male and female generative apparatus, the cavity common to the generative, 

 digestive, and respiratory functions, and a small dorsal vessel analogous to the intestinal canal of 

 Nemertes. Serpentaria, therefore, he explains, " is a composite animal, each perfect individual 

 consisting of numerous and apparently still unformed or imperfectly formed individuals." 

 Modern researches do not support any of these suppositions. Amongst the British zoologists 

 who have examined these animals, Dr. Williams, while admitting the digestive nature of this 

 chamber, misinterprets its true relations. He considers the organ a closed sac filled with a 

 milky fluid, and having many diverticula, into which the nutritive matter passes by exudation 

 from the proboscis. He appears thus to have drawn up his description from one of the Enopla, 

 which possessed no large slit leading into the chamber. He denies the existence of a proper 

 anus. While thus deviating from the true structure of the parts, he is correct at least in viewing 

 the chamber as digestive, and quite independent of the generative system placed to its exterior. 



