PROTOCOCCUS PLUVTALXS. 535 



These clear, aqueous spaces, the so termed vesicular 

 contents, are presented in all young cells, and play a 

 considerable part in cell-division, and the sap-currents ; 

 they are in all respects analogous to the vacuoles of the 

 sarcode, as already supposed by Meyen. 



Prom these considerations it would therefore appear as 

 certain as it can be made by an empirical deduction from 

 the premises in such a subject, that the protoplasm of 

 Botanists, and the contractile substance and sarcode of 

 Zoologists, if not identical, are at all events in the highest 

 degree analogous formations. 



Whence, the distinction between animals and plants, 

 viewed in the above Hght, must be thus understood ; that 

 in the latter, the contractile substance, as the primordial 

 utricle, is enclosed within a rigid, ligneous membrane, 

 which permits only an internal motion, evidenced in the 

 phenomena of circulation and rotation ; while in the 

 former it is not thus enclosed. The protoplasm, in the 

 form of the primordial sac, is, as it were, the animal 

 element in the plant, in which it is confined, being free 

 only in the Animal kingdom. Or, to express the thought 

 broadly, the energy of the organic vital activity, realised 

 in motion, is especially connected with a nitrogenous, 

 contractile substance, which, however, in the plant, is 

 " cribbed, cabined, and confined" by a rigid, inert mem- 

 brane, absent in the animal. 



The above motile attributes belong eminently to that 

 form of the primordial sac to which the author has given 

 the name of primordial cell, under which term he means 

 generally to designate that form of the primordial sac which 

 in itself assumes the figure of a cell, and is either entirely 

 without any rigid cell-membrane, or at least may exist in- 

 dependent and isolated fi'om it. Such is the case, particu- 

 larly in the Zoospores (Schwarm-sporen) of the Algae. 



This is exactly the condition presented in the primor- 

 dial cell within the enveloping cell, in the motile form of 

 Protococcus pluvialis. 



The colourless protoplasm often constitutes by far the 



