Il8 PALMKK : 



increase in bulk, cut themselves into two new drops of foam 

 each as large as the original ; and if these two daughter-drops 

 repeat the life-cycle of the mother-drop, and in turn give rise 

 to four ; and if at the end of a number of subdivisions, each 

 of the now multitudinovis drops of foam closes itself up tightly 

 in a silicious cyst and rests awhile; and if, lastly, each drop 

 again bursts its cyst and starts life anew — when all this has 

 been brought about, then perhaps we shall be willing to say 

 that the "vital force" is indeed a fetish. Then the diatom, 

 along with all the rest, may be viewed merely as a plaything 

 of the inorganic forces of light, heat, chemical attraction, 

 osmotic pressure and so forth. Meantime such views are pre- 

 mature, radical, ultra-scientific. 



The exceedingly tenacious and stubborn nature of the dia- 

 tom motion has been the subject of frequent remark. A single 

 comparatively minute Navicula or NUzschia will often create 

 great and altogether disproportionate disturbance in a drop of 

 water containing relatively long filaments of algae. Compar- 

 atively large masses of debris will be resolutely pushed aside. 

 A single cell of Euuotia, when just assuming the motile con- 

 dition and on the point of separating itself from its native fila- 

 ment ( which may be composed of a hundred cells each as large 

 as this ), will often turn the whole system of cells upside down, 

 drag it about and force it over obstacles apparently insuperable. 



The very definite and determined manner in which the 

 motile Eunotia brings itself into right relations with the solid 

 surface of the slide has been described elsewhere.''^ This phe- 

 nomenon, so significant of the real nature of diatom motion, 

 is parallelled in case of other species that are of such struc- 

 ture as to make possible their falling upon the substratum in 

 the wrong position. For instance, the larger Xavicuhr are 

 prone to fall upon their girdle sides, in which position the 

 raphes of both valves are ouf of contact with the slide. If 

 the diatoms are in good motile condition, first one and then 



*Proc. Acad. Nat. Sci., Pliil;i.. uSgS. 



