DISCOVERY OF THE PROTOZOA 107 



one of the early observers of nerve fibres and of many other 

 structures of the animal frame. His book of the protozoa 

 is a beautifully illustrated monograph consisting of 532 pages 

 of letterpress and 69 plates of folio size. It was published in 

 1836 under the German title of Die Injusionsthierchen ah 

 Vollkommene Organismen, or " The Infusoria as Perfect Or- 

 ganisms." The animalcula which he so faithfully represented 

 in his sketches have the habit, when feeding, of taking into 

 the body collections of food -particles, aggregated into spher- 

 ical globules or food vacuoles. These are distinctly sepa- 

 rated, and slowly circulate around the single-celled body while 

 they are undergoing digestion. In a fully fed animal these 

 food-vacuoles occupy different positions, and are enclosed in 

 globular spaces in the protoplasm, an adjustment that gave 

 Ehrenberg the notion that the animals possessed many 

 stomachs. Accordingly he gave to them the name u Poly- 

 gastrica," and assigned to them a much higher grade of 

 organization than they really possess. These conclusions, 

 based on the general arrangement of food globules, seem 

 very curious to us to-day. His publication was almost simul- 

 taneous with the announcement of the cell-theory (1838-39), 

 the acceptance of which was destined to overthrow his con- 

 ception of the protozoa, and to make it clear that tissues and 

 organs can belong only to multicellular organisms. 



Ehrenberg (Fig. 31) was a man of great scientific attain- 

 ments, and notwithstanding the grotesqueness of some of his 

 conclusions, was held in high esteem as a scientific investi- 

 gator. His observations were accurate, and the beautiful 

 figures with which his work on the protozoa is embellished 

 were executed with such fidelity regarding fine points of 

 microscopic detail that they are of value to-day. 



Dujardin, whom we shall soon come to know as the dis- 

 coverer of protoplasm, successfully combated the conclusions 

 of Ehrenberg regarding the organization of the protozoa. 



