THE SLUGGISH DIATOM. 1 35 



the lowermost diatom, if in contact with the substratum, 

 will scarcely move at all. The second will move nearly its 

 own length, as do the third, fourth, etc., up to the twentieth. 

 All these motions occur simultaneously. The topmost diatom 

 has then passed through a distance of twenty times its own 

 length, the next only nineteen times, and so on, the middle 

 diatom having gone the average distance of the whole group, 

 or ten times its length. The twenty diatoms, weighing just 

 twenty times as much as one, have moved ten times the dis- 

 tance traversed by each separate diatom in the same interval. 

 If one frustrule has gone at the rate of two inches per hour, 

 the group has averaged twenty inches. So that there is, after 

 all, if one could find the key to it, something in this fancy of 

 energy in proportion to volume. 



Let us return, however, to the difference in structure 

 between man and diatom. The man may be considered 

 roughly ( nt) data being at hand ) as three parts organic sub- 

 stance and one part bone by weight. The diatom, on the 

 other hand, consists by weight of possibly one part protoplasm 

 to nine of silica. Let the man, as before, weigh 170 pounds, 

 of which 128 pounds will be flesh and 40 pounds bone. But 

 a diatom of such weight would be only 17 pounds protoplasm 

 capable of propelling, and 153 pounds silica to be propelled. 

 We have calculated that a diatom of such length, if as vig- 

 orous in all its microns as its little brother of 70 /a, should go 

 0.81 mile per hour. But the 17 pounds of protoplasm does 

 all this. At the same rate the 128 pounds of human flesh, if 

 as powerful for locomotion as the diatom's protoplasm pound 

 for pound, should not only propel itself and its 40 pounds of 

 bone, at this same speed, but carry along at the same time 

 1 1 12 pounds more of inert weight. We shall permit the man 

 to dispose of this weight to the best advantage and so that it 

 shall be the least possible drag upon him, only demanding 

 that he depend alone upon his own vitality for its transporta- 

 tion. He may justly crawl along a shallow waterway and 

 have the benefit of the buoyancy and lubricatioti of the 



