HISTOLOGY OF THE LAND-PLAN AEI AN S OF CEYLON. 
155 
Fig. 2. Corresponding section to that shown in fig. 1, from Rhynchodemus Thwaitesii; 
also drawn with the camera lucida. 
The epidermis (E) shows a vertical striation, and contains four cells with 
rod-like bodies in them. The external muscular coat (E. C. M.) is very thin ; 
between the external (E.L.M.) and the internal longitudinal muscles (I.L.M.), 
and closely opposed to these latter, a band of internal circular muscular fibres 
is developed, being formed of a special development of the radiating muscles 
(R. M.) in this region of the body (see fig. 7, Plate X.). The parent glands 
of the rod-like bodies are less shrivelled by the action of spirit than in the 
foregoing preparation. 
E. Epithelial layer. 
R. Cell containing rod-like bodies. 
E. C. M. External circular muscular layer. 
E. L. M. External longitudinal muscles. 
G. Glandular mass. 
RG. Parent glands of rod-like bodies. 
I. C. M. Internal circular muscular band. 
I. L. M. Internal longitudinal muscles. 
R. M. Radiating muscles. 
Fig. 3. Vertical section transverse to the longer axis of the body through half the 
ambulacral line of Bipalium Diana, with the immediately adjoining region 
included. The side of the ambulacral line is seen to be clothed with long 
and strong cilia, which, however, fade off and almost disappear to the right 
and left in the direction of the general body-integument and in that of the 
actual inferior surface of the ambulacral line severally. The epithelial layer 
is seen to change its character entirely as it approaches the region where it 
bears the strong cilia, being there thicker and entirely free from intermixture 
with rod-like bodies ; on the inferior surface of the ambulacral line it is very 
thin indeed. The external circular and decussating muscular layer is seen to 
split into two portions — one of which is continued as a thin layer over the 
ambulacral line immediately externally to the external longitudinal muscles 
of that organ ; whilst the other, passing inwards horizontally, separates off a 
series of smaller muscular bundles from the main body of external longitudinal 
muscles, and then spreads its fibres out fanwise to become lost among the 
general muscular mass of the ambulacral line. Strong vertical fibres are seen 
to descend and end in club-shaped extremities between the external longitu- 
dinal muscular bundles of the ambulacral line. These are specially developed 
radiating fibres. 
C. Cilia. 
E. Epithelial layer. v 
E. C. M. External circular muscles. 
x 2 
