H SOCIÉTÉ BELGE 1»K MICROSCOPIE. 



movements of others of the Diatomacea? are owing to the 

 forces operating within the frustule, and are probably 

 connected with the endosmotic and exosmotic action of 

 the cells. The fluids which are concerned in those 

 actions must enter and be emitted through the minute 

 foramina at the extremities of the siliceous valves. » 



Other références are made to the subjecl, but from 

 the conclusions drawn it is évident that Professor Smith 

 had not bestowed sufficient time and attention upon the 

 movements of Diatoms, otherwise he cou Ici not hâve 

 failed to perceive that the elastic power possessed by the 

 external tubular sheath of either Gomphonema, or Schi- 

 zonema, in no way explains the movements exhibited 

 by the frustule as it leaves the tube. When a separated 

 frustule is ejected through the ruptured opening, from 

 the open extremity of the tube, it does not, as Professor 

 Smith supposed, leave the tubular sheath by any motive 

 power acquired from the elastic nature of the walls of 

 the tube ; but having acquired some other and indepen- 

 dent impetus, for as it approaches the open extremity 

 it sharply jerks itself out and swims off with increased 

 speed, quite prepared for a more active stage of exist- 

 ence. It is perfectly certain also, that the stipulate pro- 

 cesses in one genus, and presumably in ail, are émana- 

 tions from the frustules, ancl not the frustules from the 

 stipes. In the sheath of Oocconema I observée! a young 

 brood of frustules, very minute in size, closely aggre- 

 gated in a transparent subglobose plasma; not far re- 

 movcd, were a number of larger, probably older frus- 

 tules, many of which had délicate stipes attachée!, and 

 thèse, although free, exhibit no sign of motion of any 

 kind. It is probable, therefore, that the formation of the 



