HISTOLOGY OF THE LAND-PLAN AKIAN S OF CEYLON. 
117 
Kefeestein (loc. cit. xiv. 1868) employed similar methods to those here described 
for the investigation of Leptoplana tremellaris and other Sea-Planarians ; but he does 
not mention having used carmine, whence probably his somewhat imperfect account of 
the structure of the cerebral ganglia, and his failure to recognize the water-vascular 
system in Leptoplana tremellaris. There is no doubt that the use of carmine 
in such cases as this is of great assistance ; and several important anatomical details 
described in the present paper would have been missed had the preparations made not 
been stained : the water-vascular system, e. g., would probably not have been recognized 
at all. 
Max Schultze recommends a solution of chromate of potash for the preservation of 
Planarians for microscopic purposes. 
The investigation of the anatomy of such animals as Planarians, except in cases in 
which they are perfectly transparent, is only to he carried out, with any certainty as to 
results, by such methods as those here described. Schmarda and Blanchard, trusting 
to ordinary dissection with a scalpel, described series of ganglia in Bipalium ( Sphyro - 
cephalus), Schmarda (loc. cit.), and Polycladus Gayi, Blanchard (loc. cit. p. 147), respec- 
tively, which were probably in each case only the ovaries and testes, and certainly not 
ganglia, and made a number of other blunders. And Claparede’s account of the 
anatomy of Bipalium, apparently derived from the employment of similar methods, is 
very meagre and in part incorrect. The method of sections is, however, rather tedious, 
and in the course of this investigation more than forty dozen microscopic slides of 
sections of Planarians had to be prepared and preserved for careful comparison. 
Anatomy. 
For a general preliminary notion of the broader features of the anatomical arrange- 
ment of Bipalium and Bhynchodemus , reference should be made to Plate XII. figs. 1, 
2, & 3, and their accompanying descriptions. The various structural parts will here be 
considered seriatim. 
Tegumentary System. — The outermost investment of Bipalium and Bhynchodemus 
consists of a well-defined epidermic layer (Plate X. figs. 5, 6, & 7). This layer is seen in 
the figure first cited to he comparatively thin on the median line of the dorsal surface 
and that of the ambulacral line, whilst it is thicker in the lateral regions of the body. 
When the vertical section in a simple stained preparation mounted in dammar varnish 
is examined with a high power, the epidermic layer appears to be made up of a number 
of elongated elements lying closely packed together and arranged with their longer axes 
at right angles to the surface of the body. In these preparations it is impossible to 
make out any definite form amongst these elements, or any thing like a nucleus in them 
(Plate XI. figs. 1 & 2, and Plate XV. fig. 9). The cuticle of the common freshwater 
Planarian, Bendroccelum lacteum , presents in similarly prepared specimens a similar 
separation into elements by lines passing at right angles to the surface (Plate XIY. 
fig. 7, E). Occurring in this epidermic tissue are very numerous gland-cells (Plate X. 
