78 ANATOMY OF THE ENOPLA. 



organ, usually of a pale flesh or slightly pinkish hue, extending almost from the ganglia 

 to the tip of the tail, and forming (in the individuals in which the reproductive elements are 

 not developed) a lining to the body-wall, except where interrupted by the proboscidian sheath. 

 In the ripe animal, however, the gradual enlargement of the ovaries or sperm-sacs pushes in the 

 yielding organ, so that it occupies a more median position, and has its ventral portion increased 

 in bulk. It is also well to bear in mind that the body of the adult worm is only rounded in con- 

 traction, and partly so when the ova or spermatozoa are mature, but at other times it is flattened, 

 and very mobile ; thus, what is space in the transverse section is often obliterated in the living 

 animal by the collapsing and contraction of the yielding tissues in the neighbourhood. 

 Anteriorly the only opening leading into this chamber is that of the end of the rugose 

 oesophagus ; posteriorly it terminates in an anal pore, which is less easily seen than in Linens, 

 from the absence of the strongly ciliated internal streak. In intimate structure the walls of this 

 cavity resemble the anterior or oesophageal portion, only the gland-cells are larger and more 

 numerous, and the fatty elements in greater abundance, so that, although the type of structure 

 remains, there are considerable differences in microscopic appearances. I was for some time in 

 doubt about the ciliation of this chamber in Am/phiporus, since I have seldom been able to see 

 cilia satisfactorily in the uninjured A. lactifloreus, though in the latter, N. Neesii, Tetrastemma, 

 and especially Nemertes carcinop/iila, peculiar motions of the cells were apparent. When a 

 specimen is kept some time under pressure, moving granules are observed at particular 

 points ; these continue to increase in number, and sometimes a few cells accompany them, the 

 groups gradually enlarging and revolving with great velocity. Such motions are doubtless due to 

 the ciliation of the chamber. On making a transverse section of the living animal {A. lactifloreus), 

 the inner margin of the digestive cavity causes motion in the surrounding particles, but the cilia 

 are indistinct, and the appearances very different from the richly ciliated tube of Lineus, or its 

 oesophageal portion anteriorly. It is thus much more feebly ciliated than the others. 



In the walls of this complex cavity are a vast series of gland-cells, which, with M. van 

 Beneden, I consider have some analogy with the liver of the higher forms, notwithstanding 

 the adverse opinion of Prof. Keferstein, who, however, probably refers more particularly to 

 the Anopla. The cells (Plate XX, figs. 7 and 8) have an average diameter of -g-^ of an inch, 

 and consist of a delicate membrane containing a number of granular fatty bodies. After 

 extrusion from a living specimen into salt water, a remarkable movement, which the observer 

 is apt to attribute to cilia, occasionally ensues in the contents before breaking up. The contained 

 bodies jerk about within the cell, and soon a number of very minute granules appear, having 

 burst from the former, in which their presence is indicated by obscure markings. The peculiar 

 motions would seem to be due, as usual, to the action of the water, and ultimately the minute 

 structures are all set free. The various appearances of the contents of the cells are shown 

 in Plate XX, fig. 9, some being granular, others presenting faint concentric lines like starch- 

 corpuscles (though probably fatty), while three oil-globules are indicated on the right. The deep 

 port-wine oil-globule is somewhat sparingly scattered throughout the wall of the tract, the 

 yellowish-red being abundant, and the pale globule still more plentiful. These cells have a 

 similar structure in Tetrastemma (Plate XIV, fig. 13), and often escape under pressure posteriorly. 

 The quantity of deep yellow oil in this organ in T Candida is unusually great. The glandular 

 structure just mentioned undergoes partial absorption at the period of reproductive activity, so that 

 after the deposition of the ova the animal is much flattened ; but by-and-by it regains plumpness, 



