COHN PRINGSHEIM. 35 



body another name. If the. name is restricted to the internal 

 body, we cannot, in the great majority of cases, say that new 

 cells are formed in the old, but merely that they are formed out 

 of the old " (228). He agrees with Mohl, Naegeli, Unger, and 

 Hofineister, that the division of the cells into two is chiefly, if 

 not universally, the process of development of the tissues of 

 plants (233). He then gives a detailed description of the mani- 

 fold ways in which this may take place, and then enters on the 

 conjugation of cells, which leads away from our subject. 



In 1850 also, F. Conn makes some important contributions 

 to the general subject in his paper.* Here he recognizes the 

 protoplasm as the contractile element, and as what gives to the 

 zoospore (Schwarmzelle) the faculty of altering its figure with- 

 out any corresponding change in volume. The protoplasm, is 

 .said also to possess all the properties both visible in life and to 

 chemical reagents attributed by Dujardin to the Sarcode of the 

 infusoria and rhizopods. Therefore, he not only concludes 

 that the protoplasm of botanists is, if not identical, at least in 

 the highest degree analogous to the contractile substance and 

 sarcode of animals, but that this substance the protoplasm 

 " must be regarded as the prime seat of almost all vital activity, 

 but especially of all the motile phenomena in the interior " [of 

 the cell] (p. 534). With Cohn, the protoplasm corresponds 

 pretty nearly with the primordial utricle and primordial sac, 

 and primordial cell, which is simply the primordial sac assum- 

 ing the figure of a cell without any rigid cell membrane (335); 

 when a separation of cell contents takes place he calls the more 

 dense layer of peripheric protoplasm the primordial utricle as 

 Naegeli does (337). But he cannot determine with certainty the 

 presence of any nucleus in this species, and he observes that 

 the protoplasm or primordial sac can sub-divide into a number 

 of segments " without demonstrable influence of a Nucleus " 

 (543). He looks upon the flagella as prolongations of the pro- 

 toplasm, and therefore protoplasm themselves. 



Pringsheim (Untersuchuugen iiber d. Bau u. d. Bildung d. 

 Pflanzenzelle, 1854) maintains that everything that lay within 

 the cell membrane of a living cell might have a complex dis- 

 * On the Protococcus Pluvialis. Ray Society, 1853, p. 517. 



32 



