HISTOLOGY OF THE LAND-PLAN A EIAN S OF CEYLON. 
167 
PLATE XIV. 
Fig. 1. Portion of vertical section transverse to the long axis of the body of Leptoplana 
tremellaris. Drawn with the camera lucida. The section from which the 
drawing was made was cut nearly from the centre of the body of a specimen 
hardened in spirit. The portion here represented lies just to one side of the 
cavity containing the pharynx inferiorly. A portion of the water-vascular 
trunk (W) is seen in section. The external circular muscular coat (E. C. M.) 
is regarded by Keeerstein ( l. c. p. 17) merely as a basement membrane; it 
is, however, obviously homologous with the external circular muscular coat of 
Bipalium and Rhyncliodemus. 
E. C. M. External circular muscular coat. 
E. L. M. External longitudinal muscular coat. 
I. C. M. Internal circular muscles. 
I. L. M. Internal longitudinal muscles. 
V. M. Vertical muscles. 
Fig. 2. Transverse section of main water-vascular trunk of Bothriocephalus latus, copied 
from ‘ Beitrage zur Anatomie der Plattwiirmer,’ Sommer und Landois (Leipzig, 
1872), Taf. iv. fig. 1, Jc, querdurchschnittenes Seitengefass, for comparison with 
fig. 1. 
Fig. 3. Portion of a section taken in a direction transverse to the longer axis of the 
body of Bipalium Diana through the broadest part of the anterior semilunar 
extremity — that is, as it is from A to B in fig. 4. Since the digestive tract 
in this portion of the body spreads out in an arborescent manner, it is here 
seen cut through in a series of places (D, D, D). The spaces are arranged, as 
far as the drawing shows, symmetrically on each side of a central space (D / ), 
which is the direct continuation of the main median digestive tube of the fore 
part of the body. The lateral offsets are cut more and more obliquely as 
they are more and more distant from D', so that the outermost appears as an 
elongated space. Surrounding the median portion of the digestive tract is a 
large quantity of densely stained tissue, mainly glandular, which sends offsets 
downwards across the broad light space, which is the water-vascular space (W). 
The glandular tissue also spreads out laterally between the branches of the 
digestive tract and the vrater-vascular space. The water- vascular space 
stretches out to the margin of the head in the region of B, which points to 
two of the peculiar papilliform bodies which form a row along the whole 
anterior margin of the animal, and between which are the ciliated pits. The 
water-vascular space is traversed by a few stout vertical fibres and a number 
of fine horizontal fibres. A group of eyes is seen at E, on the margin of the 
animal’s semilunar extremity. Superiorly a large number of eyes are seen 
lying just beneath the epidermis, and also some pigment spots, P. At A, 
