his method of sharply discriminathig between individual 

 forms, was successfully followed by various distinguished 

 naturalists, and his systematic arrangement was the basis 

 on which they rested their observations until the year 1830. 



Although Muller deserves the high praise bestowed upon 

 him by Prof. Ehrenberg, for his generally sound philosophi- 

 cal views, his ardent desire to discover the truth rather 

 than to promote a favorite hypothesis, and the severe 

 examination to which he subjected his own opinions, yet 

 even he did not wholly escape the errors of the times : in 

 the preface to his posthumous work, he says, that animal 

 and vegetable substances, are, by decomposition, resolved 

 into vesicular pellicles, which vesicles, or globules, like the 

 crystalline globules of fungi, extend over objects in a series, 

 and form a web like that of a spider. These globules, grad- 

 ually released from the common mass, revive, and become 

 infusorial and spermatic animalcules, and from these, every 

 kind of animal and vegetable form appears to be produced.* 



Of the difficulties he had to encounter in prosecuting this 

 novel course of inquiry, he thus speaks: The difficulties 

 under which the investigation of microscopical animals 

 labors, are innumerable, and the certain and distinct resolu- 

 tion of them, requires so much time, such sharpness of 

 vision, and such acuteness of judgment, the presence of 

 so much patience and mental composure, that nothing can 

 surpass it. Nothing is easier than to see animalcules, and 

 to be delighted with their movements and sport, but to 

 perceive the differences in these most simple, active and 

 mutable little animals, in the smallest area, illuminated 

 with very few rays of light, and every moment escaping 

 from the view, and to describe in suitable language these 

 perceptions, and the various motions of each one, — 'hie 

 labor, hoc opus.' Hence after the lucubrations of many 

 hours, when I have become weary of seeing and admiring, 



* Animalcula Infusoria, Prsef. p. 24. 



