124 PALMER : 



plain enough that the inward current of carbon dioxide of 

 Kozlowski, and the outward current of oxygen of Jackson, so 

 far as these depend upon the photosynthetic reaction, will go 

 on simultaneously, will measurably balance each other, and 

 that the effect, so far as concerns motion of translation of the 

 diatom, will be nil. So that Kozlowski and Jackson, between 

 them, have merely brought it about that the diatom shall stand 

 perfectly still. 



The fact is, there has been a great deal of ingenuity wasted 

 in the endeavor to explain diatom motion as an effect of the 

 inorganic forces operating upon a vegetable cell that is capa- 

 ble of nothing but a reaction. Too much stress, in this con- 

 nection, continues to be laid upon the real and definite chloro- 

 phyll reaction. x\lso, the attraction light exerts upon the 

 diatom has been exploited in these theories beyond what is 

 reasonable. It is true that diatoms "react" in a manner 

 that is "positively phototactic " in the sense that when put 

 into a tube dark at one end and illuminated at the other, they 

 gradually assemble about the lighted end. So, also, with the 

 hen, that reacts positively to the first streak of dawn. But 

 the hen modifies her reaction at a point short of insanity, and 

 goes no farther toward sunrise than the garden where lurks 

 the early worm; and the diatom, we must conclude (since 

 diatoms still remain to us in the world ) has been able, year by 

 year, so to temper its desire for more and ever more light, as 

 to avoid very often those direct rays of the sun that are so 

 speedily fatal to it. In short, while the direction of motion 

 in diatoms is influenced by such agents as light, and this 

 motion is stimulated by oxygen and a certain degree of heat, 

 there is no reason whatever for thinking that the operation of 

 these agents "causes" the motion, or "explains" it, any 

 more than such modifying or stimulating influences cause 

 motion in any other organism. 



The egg cells of ferns secrete malic acid, and malic acid 

 is as attractive to the spermatozoids of ferns as it is to the 

 small bov who is ready to steal apples to get it. As a conse- 



