14 SOCIÉTÉ BELGE DE MICROSCOPIE. 



pther motilc organs than that of préhensile filaments 

 or other voluntary contractile bodies under the perfect 

 control of the frustule. 



At another time a minute organism belonging to a 

 différent genus would dart across the path of a Diatom 

 or corne into contact with it, vvhen it was at once 

 seized and for a moment arrested. Two Navicula 

 would cross each other, and the résultant action would 

 be of an inlermediary or restraining character, and on 

 suddenly relinquishing their hold of each other they 

 would scparate with a bound. At another lime the motive 

 action of a Diatom was seen to be ofa halting nature, 

 as if waiting to gather up its contractile organs before 

 attempting any advance. 



Light did not appear to exert any appréciable in- 

 fluence on the movements of the frustules; in fact it 

 appearcd to me that they rather avoided the sunlight 

 thrown uponthem. The application of heat, raising the 

 température of the slide some eight or ten degrees F., 

 seemed to arrest their movements, which gradually 

 became slowcr and ultimately ceased altogether. Their 

 movements wcre indeed, entirely stopped, for on trans- 

 ferring the contents of the slide to a watch-glass and 

 ad d in g a drop or two of frcsh water to it, then standing 

 it aside for twenty-four hours, the frustules on further 

 examination were found perfectly motionless and their 

 endoehromc shrunkeu and disorganised. This was pos- 

 sibly caused by coagulation of eitlier the internai albumi- 

 noïd matter, or the external protoplasmic envelope. The 

 Palmoglœa on the contrary were cven more lively, and 

 actively engaged in the process of cell-division. 



Among the contents of one cell were some fine 



