316 PROTOPLASM 



(oil membrane) and the cuticular layer. These firm threads 

 of albumen are supposed, on their part, to arise by the 

 action of oxygen upon the dissolved albumen, which, as 

 Quincke has shown in the case of egg albumen, forms a firm 

 membrane-like envelope under the action of this gas. The 

 firm threads of albumen which have arisen in this manner are 

 supposed to be torn loose by the streaming movements and 

 to be carried into the interior of the cell, where they form 

 an internal framework traversing the cell sap. As they are 

 torn loose the filaments take with them an envelope of oil 

 from the oil membrane. In consequence the protoplasmic 

 masses are then free to move upon these oil-covered fila- 

 ments by means of extension-currents, in the same way as 

 the protoplasm of the wall moves upon the external oil mem- 

 brane. In the same manner Quincke thinks the fine pseudo- 

 podia of Sarcodina may also be explained, since he remarks 

 (p. 641): "The pseudopodia appear to be just such thin 

 filaments of albumen covered with oil, along which solid 

 albuminous granules are carried up and down by periodic 

 extension movements, just as in the interior of the plant cell." 

 Although there is, perhaps, much to be said for this concep- 

 tion in the case of the explanation of the so-called granular 

 movement on the pseudopodia, yet it in no way explains 

 the formation of the fine pseudopodia themselves. For 

 both their gradual development and the formation of 

 bridges and filaments of protoplasm in the cell sap of plants, 

 which, according to the statements of many trustworthy 

 observers, frequently develop just like the pseudopodia of 

 Sarcodina, make it impossible to refer their origin to the 

 breaking loose of solid threads of albumen, which the 

 streaming movements displace as pseudopodia. 



As far as Quincke's interpretation, which we have just 

 quoted, of the pseudopodia themselves is concerned, it may 

 perhaps be justifiable to a certain extent, inasmuch as we 

 have already seen that the study of the pseudopodia had 

 long ago led M. Schultze, and again myself also recently, to 

 the supposition that possibly a firm thread may form the 

 axis of the pseudopodium a supposition to which their 

 analosrv with the state of things in the Heliozoa adds 



Oi/ O 



