HISTOLOG-Y OF THE LAND-PLAN ASIANS OF CEYLON. 
143 
short distance posteriorly from the anterior fluid extremity. In the female portion of 
the generative organs there is no definite vaginal tube as in Bipalium. The uterus forms 
a much larger cavity, and the oviducts here unite into a single tube instead of remaining 
distinct like those of Bipalium, and they enter the posterior wall of the organ instead 
of the anterior. 
Looking at the testes and ovaries as shown in Bipalium (Plate XII. fig. 1), there can 
be little doubt that these are the ;c ganglia” which Schmarda described, the ovaries being 
the first pan. Moreover, Blanchard’s similar ganglia in Polycladus are almost certainly 
due to the same cause : the especially large ganglia in what he calls the tail of his 
animal, but which in reality, as explained by Max Schultze, was the head, is evidently 
the ovary, and the remainder of the ganglionic chain the testes. Polycladus must 
therefore be closely related to Bipalium in the arrangement of its generative organs. 
Nervous System. — There is no trace of the series of ganglia described as existing in 
Bipalium by Schmarda, other than the ovaries and testes. After most careful examination 
I could not discover anything like a ganglion-cell in the whole body of either Bipalium 
or Bhynchodemus. I believe that the nervous system, which is in these Planarians 
very indistinctly differentiated histologically, forms a meshwork within the primitive 
vascular canals. In the head such a meshwork is to be observed, in sections made from 
specimens hardened in chromic acid, occupying the same region and having the same 
form as the vascular ramifications in the head. A portion of this meshwork is figured, 
Plate XY. fig. 5. The dark matter at the points of union of the bundles of fibres is 
merely finely granular in structure and has no cell-structure. Similar tissue may be 
traced along the whole length of the body in the primitive vascular canals, both in 
Bipalium and Bhynchodemus. After very careful examination I have been able to 
discover no more specialized nervous system in these Planarians than this. The fine 
threads within the vascular canals in the penis of Bipalium are probably nerves ; and in 
Bhynchodemus an undoubted and distinct nervous filament is given off from the inner 
extremity of the eye (Plate XY. fig. 8), but it cannot be traced to connexion with any 
definite nervous structure ; it passes to the main vascular trunk and is there lost. In 
order to make certain that ganglia such as those known to exist in other Planarians 
were really absent in Bipalium and Bhynchodemus , and had not merely been destroyed 
by the method of treatment, I prepared sections from a specimen of Leptoplana tremel- 
laris hardened in spirit in the same manner as my Land-Planarians, so as to display the 
structure of the nervous ganglia. Figs. 1, 2, 3, & 4, Plate XY., represent four longi- 
tudinal and horizontal sections from this specimen drawn with the camera lucida, and 
are given here to show the remarkable complexity of the structure of the ganglia in this 
Planarian, and the very great distinctness of the ganglion-cells. Most certainly no 
such structure as this exists in Bipalium or Bhynchodemus. 
It is constantly asserted by older and even by modern writers that ganglion-cells do 
not exist in Planarians and Nemertines (Frey and Leuckart, loc. cit. p. 92 ; Leydig, 
Yom Bau des thierischen Korpers, p. 124). Quatrefages (Sur les Planaires, p. 172) 
