CHAPTER II 

 HISTORICAL SKETCH 



For the purpose of presenting in brief compass the main pub- 

 lished observations and experiments on ameboid movement, we 

 may pass from the observations of v. Rosenhof, mentioned in the 

 introduction, to certain observations which Wallich ('63) 

 recorded. He found that a new pseudopod is usually formed as 

 a small break in the ectoplasm somewhere on the ameba through 

 which the endoplasm then flows. As the endoplasm flows out 

 and the new pseudopod enlarges, the breach in the ectoplasm in- 

 creases in extent, through a transformation of the ectoplasm in 

 the immediate vicinity of the breach, into endoplasm. But he 

 observed also that some of the endoplasm which flows into the 

 new pseudopod becomes transformed into ectoplasm. Wallich 

 thus demonstrated that ectoplasm and endoplasm are mutually 

 convertible. 



The conversion of ectoplasm into endoplasm and vice versa, 

 was regarded by Wallich, however, as a process taking place only 

 occasionally, such as when new pseudopods are formed. It re- 

 mained for Biitschli ('80, p. 115) to point out that in a moving 

 ameba endopasm is continually formed from ectoplasm at the 

 anterior ends of all pseudopods, while the reverse process, viz., 

 the conversion of ectoplasm into endoplasm, takes place continu- 

 ally at the posterior end of the ameba. He describes the relation 

 of ectoplasm to endoplasm as a ''circulation" ; the endoplasm, ar- 

 riving at the anterior end, becomes changed into ectoplasm, which 

 after remaining relatively stationary for a while on the outer side 

 of the animal, soon finds itself at the posterior end of the ameba, 

 where it is slowly changed into endoplasm. The movement of 

 the endoplasm forward to the anterior end of the ameba completes 

 the cycle. 



In 1898 Rhumbler, from observations on several species of 

 amebas, came to the conclusion that in the change from ectoplasm 

 into endoplasm, and vice versa, must be sought the cause of ame- 

 boid movement. 



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