124 LAY SERMONS, ADDRESSES, AND REVIEWS. [vu 



the hair which it fills. When viewed with a sufficiently 

 high magnifying power, the protoplasmic layer of the 

 nettle hair is seen to be in a condition of unceasing 

 activity. Local contractions of the whole thickness of 

 its substance pass slowly and gradually from point to 

 point, and give rise to the appearance of progressive 

 waves, just as the bending of successive stalks of corn by 

 a breeze produces the apparent billows of a corn-field. 



But, in addition to these movements, and independently 

 of them, the granules are driven, in relatively rapid 

 streams, through channels in the protoplasm which seem 

 to have a considerable amount of persistence. Most 

 commonly, the currents in adjacent parts of the proto- 

 plasm take similar directions ; and, thus, there is a 

 general stream up one side of the hair and clown the 

 other. But this does not prevent the existence of partial 

 currents which take different routes ; and, sometimes, 

 trains of granules may be seen coursing swiftly in 

 opposite directions, within a twenty-thousandth of an 

 inch of one another ; while, occasionally, opposite streams 

 come into direct collision, and, after a longer or shorter 

 struggle, one predominates. The cause of these currents 

 seems to lie in contractions of the protoplasm which 

 bounds the channels in which they flow, but which are 

 so minute that the best microscopes show only their 

 effects, and not themselves. 



The spectacle afforded by the wonderful energies 

 prisoned within the compass of the microscopic hair 

 of a plant, which we commonly regard as a merely 

 passive organism, is not easily forgotten by one who has 

 watched its display, continued hour after hour, without 

 pause or sign of weakening. The possible complexity 

 of many other organic forms, seemingly as simple as 

 the protoplasm of the nettle, dawns upon one; and the 

 comparison of such a protoplasm to a body with an 



