96 JOURNAL OF THE [Octobcr, 



contact with the diatom, and about half-way freed from its end. 

 Now, while the diatom was at rest, the globule, without any 

 motion of its own, was transported back to a point under the 

 central nodule of the diatom. After resting there a moment it 

 was carried back to the free end of the diatom. Meanwhile the 

 diatom freed itself from the obstruction, and the globule was 

 liberated, and I then again saw that the globule was inert and 

 incapable of motion of its own. Therefore it is reasonable to 

 suppose that its motion was due to a propelling influence exerted 

 over it by the exoplasm of the Navicula viridis. 



With regard to the momentum of the diatom in motion, I saw 

 a rapid traveller, a small Navicula radiosa, forge along and strike 

 a large, quiet JV. viridis about the middle, with such an impetus 

 as to throw the IV. viridis through an arc of more than forty-five 

 degrees to the left of the point of impact It immediately re- 

 gressed after the shock. The mathematical physicist could tell 

 the nature of the impact — as impact is a resultant of weight and 

 velocity, and motion is the opposite of inertia, one indicates life 

 and action, the other inability to change position without some ' 

 extraneous force. 



Still drawing upon my study of the Whistler fresh-water gath- 

 ering, I examined closely the behavior of the " tetradelphia " 

 groups of Naviculae. I observed that the quadruple brotherhood 

 of so-called single cells could turn around in their own length, 

 that they could also travel in straight lines, and that if capsized 

 or thrown on their " beam ends " they struggled to bring them- 

 selves to the normal position of bodies swimming horizontally. 

 While they were struggling to regain the plane of flotation I was 

 enabled to study them in every aspect. In these frustules the 

 characteristic endoplasm, endochrome, oil globules, vacuoles, 

 etc., were clearly seen, more particularly through the cingula, or 

 connecting band, as this is less lined than the frustular faces. 

 This combination of four frustules would seem to suggest that 

 the directive force of the quadruple frustules is controlled largely 

 by the two external frustules, and for the four to move in a 

 direct line the protoplasmic, propelling force (?) must be syn- 

 chronous in all four; and when it is not so, or when the quadruple 

 frustules are moving in a circle of their own length, the rapid, 

 undulatory vibrations of the protoplasmic sheath of the two 



