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A journey of discovery in this wonderful labyrinth would be 
certainly in the highest degree attractive and instructive; but we 
should find it too difficult. Instead of this, it answers our purpose 
far better, to cast a glance at the very szmply built soul-apparatus 
of a lower animal. We choose for this purpose a simple worm ; 
not because man, according to Faust, “‘is like a worm that grubs 
through the dust,” or because according to modern phylo-genetic 
theories, there is in the genealogical tree of men even a row of 
worms among our ancestors, but rather because in the lower worms 
there is exhibited a very simple and clear building-up of their soul- 
organ, which excellently facilitates the difficult comprehension of 
the highly constituted soul-apparatus of the higher animals. 
Let me observe such a single worm, e.g., a leaf-shaped plan- 
arian or turbellaria, under the microscope. We observe in front, 
over the mouth, a tiny white ball, from which fine threads radiate 
in all directions to the various parts of the body. That white ball 
above the mouth consists of a soft nerve mass, and is the centre of 
the whole soul-apparatus, in fact, a dvazz of the simplest kind; and 
the fine threads which radiate from the brain to all parts, are 
nerves. We distinguish two sorts of such nerve threads. One sort 
are instruments of the will, motor or efferent nerves; they go from 
the brain to the flesh, the filaments of which, instead of the muscle- 
filaments, are excited by them to movement. The other sort are 
instruments of sensation, or sensory nerves: they carry the different 
impressions of sensation from the outer skin, and from the organs 
of sense to the brain, and thus place the latter ex rapport with the 
surrounding outside world. The instruments of sense of such a 
lower worm are certainly as yet very simple, but it is just on this 
very account that they are so interesting. In many worms it is 
simply and alone the outer skin which supplies the place of a 
general sense instrument, and communicates sensations of various 
kinds, especially variations of pressure and of temperature. In 
others there are added, eyes of a very simple kind, dark spots 
in the skin, which surround a refracting lens; also organs of 
hearing of a very simple form, viz., a pair of little dimples or 
bladders in the skin, which are thickly set with fine little hairs ; 
