76 THE ANATOMY OF AN AUSTRALIAN LAND PLANARIAN. 
In brief, the life-history of the rod-like bodies appears to be as follows:—They 
originate as condensations of the protoplasmic body of small, nucleated, spimdle-shaped 
mother cells which lie beneath the special zone. As they merease im size and 
numbers they destroy the mother cell and themselves accumulate, still arranged in 
bundles, in the special zone. Hence they gradually pass outwards towards the surface 
of the animal, and again accumulate between the cells of the epidermis. Finally they 
are discharged and come to lie freely in the slimy covering of the animal. . 
The most remarkable feature of the rod-like bodies m Geoplana spencer: stall 
remains to be noticed. Moseley (1) has already observed, when speaking of the 
Australian land Planarians, that ‘‘ The remarkable Prussian blue-coloured Cenoplana 
cerulea has its intense pigment contamed to a large extent im the rod-cells, which 
stand out thus in relief in the vertical sections of the animal.” If for ‘‘ rod-cells” we 
read ‘‘rods” the same remark applies exactly to Geoplana spencer; the rod-like 
bodies, in unstained sections, appearing of an intense blue colour, so that the special 
zone contaiing them stands out brilliantly. The colouring matter appears to be 
evenly dispersed through the rods, and it makes its appearance while the latter are 
still very minute and lying beneath the special zone. 
With regard to the function of the rod-like bodies, various hypotheses, none of 
which are at all satisfactory, have been suggested. Ido not propose to discuss the 
question here, and it will probably have to be decided by careful experiment on the 
living animals. In an earlier portion of this paper I have suggested, however, that 
they may possibly, by making the animal extremely unpalatable, serve as a protection 
against being eaten.* 
H1.—The Nervous System.—Previously to the year 1879, the greatest doubt and 
uncertainty prevailed with regard to the nervous system of laud Planarians. The 
existence of two longitudinal cords was admitted, though not by all naturalists, but 
their nature was greatly misunderstood. In 1879, however, a flood of light was 
thrown upon this much vexed question by von Kennel’s researches on the German 
land Planarians. (3) Itisno longer necessary to discuss the various views entertained 
prior to this date ; I will simply take up the question where von Kennel leftit. This 
author recognised the existence of an anterior ganglionic mass (‘‘Gehirn”’), 
composed of two symmetrical halves and containing nerve cells. He also 
recognised the connection of this ganglion with the two longitudinal nerve cords, 
which run parallel beneath the alimentary canal to the posterior end of the 
body, and are connected with one another by numerous transverse commissures, 
at the same time giving off numerous branches. 
I had convinced myself that this was the true state of the case before I saw von 
Kennel’s paper, in which he so completely forestalled me. All that I can now add 
* They may also serve to increase the stickiness of the slime, and thus enable the animal to hold its prey more firmly. 
(Vide p. 53.) 
