HISTOLOG-Y OF THE LAND-PLANAKIANS OF CEYLON. 
169 
Fig. 6. Small portion of the main water-vascular trunk of Bipalium Diana , as seen in 
vertical section. Drawn with the camera. Three muscular bands are seen 
traversing the portion of the water-vascular trunk here represented, and they 
are crossed diagonally by several finer muscular fibres. The interstices 
between these two sets of fibres are filled with a close network of very fine 
fibres, bearing here and there small nuclei. The darkly stained irregularly 
shaped masses (X, X) send out finely ramifying processes, which become lost 
amongst the fine fibres forming the general meshwork, and apparently anas- 
tomose with them. 
V . M. V ertical muscular fibres. 
D. M. Diagonal ditto. 
X, X. Irregular protoplasmic bodies. 
Fig. 7. Main trunk of the water-vascular system, of Dendrocoelum lacteum in vertical 
section, with adjoining tissue, from a section corresponding to that represented 
in fig. 8, Plate X., but more highly magnified. Drawn with the camera. 
The water- vascular trunk (W), which is here divided into two by a stout 
vertical muscular fibre, is seen to be filled with a network of extremely fine 
fibres, some of which have minute nuclei upon them. The open spaces in 
the meshwork are irregularly oval. The oviduct (OD.) immediately above 
the external portion of the water- vascular trunk is seen to be made up of 
definite nucleated cells, as in Bipalium and Bhynchodemus ; it is imbedded 
in a mass of fusiform cells and stroma. The vertical muscular fibres (V. M. ) 
pass downwards between the longitudinal muscles (L. M.), and unite with the 
circular muscles (C. M.). 
y. M. Vertical muscular fibres. 
OD. Oviduct.] 
W. Water- vascular system. 
L. M. Longitudinal muscles. 
C. M. Circular muscles. 
E. Epithelium. 
Fig. 8. The papillae of Bipalium Diana , as seen in a thin section shaved off from the 
anterior margin of the animal’s head, and viewed directly from the front, and 
magnified more highly still. Compare Plate XIII. fig. 17. 
A. Openings of the ciliated pits between the upper extremities of the 
semicolumnar projections, of which four are here displayed. 
PLATE XV. 
Figs. 1, 2, 3, 4. Series of longitudinal sections in the plane of the body through the 
cephalic ganglionic masses of a Sea-Planarian, Leptoplana tremellaris , from a 
specimen preserved in spirit ; drawn with the camera lucida. The series, as 
mdccclxxiv. z 
