ECONOMIC IMPORTANCE OP DIATOMS— MANN. 383 



with these organisms, namely the value they have in throwing light 

 upon a study of the differences between objects which are the product 

 of mere mechanical construction and those the construction of which 

 is coordinated with life. There are two things to be said in regard 

 to the ornamentation of these plants. First, there is a perfection at- 

 tained that is essentially absolute, and yet not so servilely exact to the 

 type as to preclude the marks of individuality in each separate plant. 

 Take a diatom, upon the surface of which are found some hundreds 

 of glittering hemispherical beads, and a careful examination with 

 the finest optical apparatus will discover no trace of crudity or 

 irregularity in these hemispheres, each one being polished Avith a 

 perfection and curved w^ith an accuracj^ that is absolute; and yet it 

 would be hard to find two individuals with the same number of beads. 

 Among the thousands of these organisms that can be found in a 

 spoonful of ooze dredged from the bottom of the sea and extending 

 for thousands of miles beneath its waters, each separate form will 

 show the same adherence to its type, the same perfection in its work- 

 manship, but the same unmistakable individuality. This is not 

 mere mechanical accuracy, but an accuracy associated in some un- 

 known way with the qualities of that master builder within each 

 cell, cytoplasm. The distinction here insisted on is precisely that 

 between the flight of a bullet and the flight of a bird. It is well illus- 

 trated by the contrast to be seen in two of the accompanying illustra- 

 tions ; the sculpture of the living organism being shown in the figure 

 of SurireUa haldjikii copied from a photograph of that diatom, while 

 the sculpture represented in the figure of a very similar diatom, 

 Surlrella gracilis^ is a mechanicalh^ drawn counterfeit. How this 

 living, almost formless jelly, plays the role of a peerless artificer it 

 still remains for science to discover. 



The other point in a study of the structure of these organisms is 

 that the principles of design are sui generis and not at all associated 

 with the substance of which they are composed. Silica, like all other 

 mineral matter, has its definite lines and angles of crystallization ; so 

 that a particle from one part of the world fits with infinite nicety 

 into a particle from any other part of the world. But this silica is 

 woven on the looms of the diatoms into fabrics the mesh of which 

 may be one of many thousand patterns, and no principle of curves and 

 no combination of lines Icnown to geometry correspond in the slightest 

 degree to those found in the ornamentation of these plants. For ex- 

 ample, a line may begin straight, bend gently into a curve, gradually 

 or instantaneously be changed again and thus make up, with the 

 thousands of other lines of the pattern, a variety of arrangement that 

 has no relationship to the principles of mathematics. And yet there 

 is a law vrithin this apparent lawlessness so rigid that the individual 

 species hold their characteristics through thousands of years, and 



