CHAPTER VI 

 THE SPECIES QUESTION 



After the discovery of the ameba by Rosel v. Rosenhof and the 

 introduction of the Linnean system of nomenclature, the number 

 of new species of amebas that were reported increased rapidly. 

 But in 1856 Carter suggested that what had been described as 

 A. radiosa probably was a young stage of A. protcus. With the 

 general acceptance of the Darwinian Natural Selection Hypothesis, 

 the ameba came to be looked upon as standing at the bottom of 

 the scale of organisms, and consequently was supposed to lack 

 generally such characters as the higher forms possessed. The 

 ameba became the representative of the "primordial slime" from 

 which by slow stages the other organisms were evolved. So of 

 the sixty odd species which had been described up to Leidy's 

 ('79-) time, Leidy, following the suggestion of Carter, was in- 

 clined to think that the great majority of these represented only 

 changes of shape of about four species (not including the several 

 species that were then known to be parasitic). Since Leidy's time 

 the prevailing tendency has been to regard most of the ''new" 

 species as mere environmental or life cycle stages of a very few 

 species. A very noted exception to this tendency, however, has 

 been Penard's ('02) great work on the amebas and other rhizo- 

 pods of the Leman Basin, in which he describes forty-five species 

 of amebas (including Gloidium, Protamoeba, Amoeba, Dinamoe- 

 ba, Pelomy.va), paying attention mainly to the readily observed 

 ectoplasmic and endoplasmic characters, and the appea r ance of 

 the resting nucleus. 



The remarkable discoveries of Vahlkampf ('05) of the nuclear 

 changes during the division process turned the attention of nu- 

 merous investigators to this field, and the ectoplasmic and endo- 

 plasmic characters thenceforward received scant attention. Thus 

 Calkins ('04) came to. suggest as Carter had done many years 

 before, that A. radiosa was merely a young form of A. protcus. 

 And Doflein ('07) intimated that the protoplasmic characters of 



