Translation from Von Hartmann 109 



gence stand far below the higher plants — to which, indeed, 

 any kind of deliberative faculty is commonly denied. Even 

 in the case of those minute microscopic organisms that 

 baffle our attempts to classify them either as animals or 

 vegetables, we are still compelled to admire an instinc- 

 tive, purposive behaviour, which goes far beyond a mere 

 reflex responsive to a stimulus from without ; all doubt, 

 therefore, concerning the actual existence of an instinct 

 must be at an end, and the attempt to deduce it as a con- 

 sequence of conscious deliberation be given up as hopeless. 

 I will here adduce an instance as extraordinary as any 

 we yet know of, showing, as it does, that many different 

 purposes, which in the case of the higher animals require 

 a complicated system of organs of motion, can be attained 

 with incredibly simple means. 



Arcella vulgaris is a minute morsel of protoplasm, which 

 lives in a concave-convex, brown, finely reticulated shell, 

 through a circular opening in the concave side of which 

 it can project itself by throwing out pseudofodia. If we 

 look through the microscope at a drop of water containing 

 living arcellcB, we may happen to see one of them lying 

 on its back at the bottom of the drop, and making fruit- 

 less efforts for two or three minutes to lay hold of some 

 fixed point by means of a pseudopodium. After this there 

 will appear suddenly from two to five, but sometimes 

 more, dark points in the protoplasm at a small distance 

 from the circumference, and, as a rule, at regular distances 

 from one another. These rapidly develop themselves into 

 well-defined spherical air vesicles, and come presently to 

 fill a considerable part of the hollow of the shell, thereby 

 driving part of the protoplasm outside it. After from 

 five to twenty minutes, the specific gravity of the arcella 

 is so much lessened that it is lifted by the water with its 

 pseudopodia, and brought up against the upper surface 

 of the water-drop, on which it is able to travel. In from 

 five to ten minutes the vesicles will now disappear, the 

 last small point vanishing with a jerk. If, however, the 



