io8 HISTORY OF BOTANY 



real basis of the cell, it began to dawn upon the botanists 

 that the slimy contents of the vegetable cell, so like the 

 sarcode in general appearance, might turn out to be 

 something of the same nature, if not identical with it. 

 Von Mohl, in 1844, took the plunge and boldly announced 

 that the slimy lining — " primordial utricle '* he called it — 

 of the vegetable cell was a living substance and was the 

 primary and most important constituent of the cell, and 

 gave it the name of " protoplasm," a term he borrowed 

 from the human physiologist Purkinje, who had so 

 designated the granular substance of the animal ovum 

 in 1840. The final step was not a difficult one, though 

 it is somewhat doubtful to whom belongs the credit of 

 having first taken it. Perhaps it would be fairest to say 

 that the conception of the identity of sarcode and proto- 

 plasm was in the minds of several workers during the 

 years 1845-55, but more especially in those of Max 

 Schultze and Unger. When motile gonidia were found to 

 be destitute of cell walls, and when^-De Bary had shown 

 that cell walls were absent from the Mycetozoa, it became 

 at once apparent that the wall was quite a subordinate 

 feature of the cell and that the real cell consisted of 

 a mass of protoplasm with a nucleus, an " energid," 

 as it was afterwards termed, a view now held by all 

 biologists. 



Here then at last was the " vehicle of irritation " 

 dimly hinted at by Knight, the real seat of the " vital 

 force '* beheved in so firmly by the physiologists of the 

 closing years of the eighteenth century, the " physical 

 basis of hfe," as Huxley called it many years afterwards, 

 and all the associated structures such as cell walls, vacuoles, 

 oil drops, starch grains, microsomata, and so on, at once 

 fell into their appropriate places as subordinate products 

 of the activity of protoplasm. The so-called *' vital 

 sap " was thus seen to be protoplasm, and the movements 

 in it were correlated by Alexander Braun and De Bary 

 with the locomotory movements of free zoogonidia and 



