MÉMOIRES. 13 



time I shared in this view but further observations hâve 

 changea* my opinion. The very gênerai distribution of 

 cilia and flagella among the lower as well as higher 

 organisms, is, liable to affect one's judgement; that 

 exquisite example amongst unicellular plants, the Volvox 

 globator, the enveloping membrane of which is perfo- 

 rated in every direction by an endlcss number of cilia, 

 being a noteworthy example. 



In once again entering upon the investigations of the 

 movements of Diatoms, I bave been anxious to divest 

 myself of ail preconceived opinions, of either cilia or 

 other organs, and having obtained during the past sum- 

 mer a bountiful supply of lively spécimens, I at once 

 made them the subject of careful and prolonged study. 

 Portions taken from the bulk, together with cells of 

 Palmoglœa, were transferred to a growing slide, the 

 last named being arranged in groups of from two to a 

 dozen or more primary cells. By expansion of the trans- 

 parent outer membrane thèse cells soon displayed the 

 phenomenon of self-division ; but neither in the com- 

 pound state, nor as single cells did any of them exhibit 

 any other kind of motivity. The Diatoms on the conlrary 

 were incessantly on the move, passing to and fro, 

 over the field of the microscope. Now and again they 

 would seize upon a Palmoglœa and carry it off. Any 

 retraction of the contractile filament of the Diatom pro- 

 duced a sudden jerky movement of the cell; but as 

 soon as it relinquished its hold it retumed to a state of 

 perfect rest. Occasionally a fresh attack was made and 

 the cell was scen to follow in the track of the Diatom. 

 The movements were so remarkable, that no one obser- 

 ving them, could, I venturc to think, refer them to 



