16 Dr. G. C. Wallich on the Diatomacea. 



Having been "towed" along as just described, the particle 

 may all at once be suddenly drawn towards or upon the Diatom, 

 when similar phenomena to those above noted are perhaps 

 again repeated. 



At times the course of events is changed. The Diatom 

 cleaves its way, and evades or pushes through an obstacle which 

 is sufficient to check the particle it happens to be dragging 

 behind it. We now see the Diatom suddenly arrested, at the 

 precise instant that the obstacle is observed to take effect upon 

 the particle. Again the Diatom jerks, as if endeavouring to 

 free the obstructed particle by dragging it through the obstacle, 

 and again every jerk and movement are most faithfully repeated 

 by the particle in tow and also by the obstacle it is impeded by. 

 Should the force exercised prove insufficient to release the par- 

 ticle, one of two events occurs : either the bond of union, what- 

 ever it may be, appears suddenly to break or relax, and the Dia- 

 tom springs forward on its course ; or, at the end of the usual 

 alternating interval, the bond of union being still retained, the 

 frustule retraces its steps. 



In this last event, a very remarkable phenomenon may be 

 witnessed. The Diatom either manages to pierce or to evade 

 the obstacle which impeded the particle it had ' ' in tow/' and 

 frees it by causing it to recede from instead of advancing through 

 the obstacle ; or, having released its hold, it advances alone, 

 leaving the particle motionless. Sometimes the Diatom appears 

 to " anchor " itself to a spot, and the particle, should one be 

 retained " in tow," instantly stops. But, although at a con- 

 siderable distance, it may be observed to experience jerks and 

 movements utterly incompatible with any forces except such as 

 must originate with the Diatomaceous frustule. Or, although 

 the frustule is evidently anchored in some way, and thus enabled, 

 generally speaking, to withstand the recoil shock or jerk due to 

 the force it has applied, the unmistakeable connexion between 

 some jerk of the particle it is applied to and the corresponding 

 recoil the frustule exhibits leaves no possible room to deny the 

 sequence of the two events as cause and effect. And, lastly, the 

 whole of the above phenomena may occur between a frustule and 

 one or many such particles of matter. 



These, then, constitute some of the most striking appearances 

 which bear directly on the problem before us. In avoiding the 

 complications that must have arisen had I attempted to depict 

 all the modifications they are liable to under a variety of acci- 

 dental circumstances of no significance one way or the other as 

 relates to the point to be proved, I should have become simply 

 unintelligible. 



The view entertained by Professor Smith, and indeed by the 



