The Ciliiim. 181 



held earlier. He did not, however, try to support it by direct proof, 

 but laid it down, rather, as a hypothesis upon which to base his 

 observations and speculations upon the structure and moA^ements of 

 protoplasm. According to him, protoplasm is an emulsion ; that is, 

 it is a mixture of two or more complex fluids (''Der Plasmakorper in 

 seiner Gesammtheit als eine Emulsion von mehr odor woniger fliis- 

 siger Consistenz aufzufassen ist." (Berthold 1886, p. (54.) 



Quincke (1870 and later) also held that protoplasm was a fluid, 

 but after Biitschli's publication seemed to favor the foam theory. It 

 was from Quincke that liiltschli got the idea of foams which figure 

 so prominently in his conceptions of protoplasm, but Quincke does 

 not seem to have made the application of his foams to protoplasm 

 until after Biitschli published. 



Schwartz, another writer of this period (1897), seems to hold to 

 the view of protoplasm as fluid, but, as Biitschli points out, it is diffi- 

 cult to understand just what his position is. 



In recent years Verworn, Rhumbler, Jensen, Loeb, Gurwitch and 

 many others have supported this view. 



BiJTSCHLI^S SCHAUME. 



Very early Biitschli, as has been noted above, objected to the con- 

 traction theory of protoplasmic movements, and in 1887 we find him 

 advocating the fluid nature of the endosarc of the Infusoria. Later 

 (1892) he came out with a definite theory of the structure of proto- 

 plasm. According to him, the key to its structure is to be found in 

 the microscopic oil-foams. The first fifty-seven pages are given up to 

 the investigation of foams of different kinds. After an extensive 

 study of the protoplasm of a large number of protozoa, of bacteria 

 and of cells of many animal tissues, he concludes that its structure 

 corresponds to that of the minutest microscopic foams. ('^ISTach 

 meiner Auff'assuug entsprach der Aufbau des Plasmas den micro- 

 skopischen Schaiimen mit dem TJnterschied, dass der Wabeninlialt 

 gewohnlicher Schaume liingegen eine wiisserige Fllissigkeit sei." Biit- 

 schli, p. 3.) In the application of this concei^tion to the explanation 

 of protoplasmic movements he admits that, while it is satisfactory for 

 amoeboid movement in the strict sense, modifications of it, especially 



