10 THE PROTOZOA 



geal ganglion of the rotifers (cf. Fig. 11). He discovered the 

 myonemes or muscular elements in the stalks of Vorticella, in Stentor, 

 and in certain other Ciliata, and interpreted them as muscles. He 

 discovered that the flagellum of the flagellates is the motile organ, 

 but explained its vibrations as due to the action of exquisitely fine 

 muscle-fibres. Pigment spheres and protoplasmic granules were de- 

 scribed as ovaries, the nucleus as a testis, while the contractile 

 vacuole was at first regarded as a respiratory organ. With this latter 

 conclusion he could not harmonize his subsequent observations, and 

 finally decided that the vacuoles have the same functions as in the 

 rotifers. 



Ehrenberg's strong position as an investigator of Protozoa is due to 

 his remarkable powers of observation, especially of the finer structure 

 of flagellates and ciliates, which in many cases he described and 

 accurately figured, and these justify the tribute which Butschli pays 

 him: 



"The great service which Ehrenberg did in furthering the knowledge of these 

 forms cannot be clearly enough recognized. After a naturally somewhat difficult 

 comparison, I find among the species described in 1838 a few more than 100 Infusoria 

 (in the present sense), of which five are Suctoria. Also his system of classification 

 was much more natural than that of any of his forerunners, and formed the basis of 

 all subsequent efforts. Many of his genera had correct limitations which hold even 

 to-day, although many indeed cannot be sustained. . . . With astonishing assiduity 

 he sought to collect, study, and systematically interpret everything that had been 

 done upon the Infusoria." ('83, p. 1145.) 



Ehrenberg's interpretations, however, were not as successful as his 

 collection of data, and it is to be regretted that throughout his life he 

 obstinately clung to his view of the Poly gas trie a, even after the period 

 of the complete establishment of their unicellular nature. It was 

 surely the irony of fate which led to the publication of his immense 

 work on the Polygastrica the same year ('38) that the Dutch botanist 

 Schleiden made the greatest advance in the conception of the cell as 

 the unit of structure. 



A formidable opponent of Ehrenberg soon appeared in France, 

 Felix Dujardin, who, influenced by long study of the Rhizopoda (or 

 Protozoa with changeable processes), came to the conclusion, in 1835, 

 that the marine forms (Foraminifera), which, up to that time, had 

 been classed with cephalopod molluscs, are in reality the simplest of 

 organisms, composed of a simple, homogeneous substance which he 

 called sarcode. He showed that the many stomachs, which, according 

 to Ehrenberg, constituted the digestive tract, were mere vacuoles 

 without definite walls, which become filled with water taken in from 

 the outside with the food. He denied Ehrenberg's assertion that an 

 anus terminates the digestive tract, although in some cases his gener- 



