Vol. LII June, 1927 No. 6 



BIOLOGICAL BULLETIN 



OBSERVATIONS ON THE LIFE-HISTORY OF 

 AMCEBA PROTEUS. 1 



H. R. HULPIEU 



IN COLLABORATION WITH 



D. L. HOPKINS, 

 ZOOLOGICAL LABORATORY, THE JOHNS HOPKINS ("XIVERSITV. 



There is still considerable diversity of opinion concerning the 

 life-history of Amceba proteus. Some hold that it reproduces 

 exclusively by binary fission ; others do not agree with this. 



Carter ('56) asserts that he observed the nucleus in a given 

 specimen, break up into several small nuclei each of which as- 

 sociated itself with a bit of cytoplasm; and that he then saw the 

 membrane ot the amoeba break and the small nuclei with their 

 surrounding cytoplasm escape into the external medium and 

 move away by amoeboid movement. 



Wallich ('63), Scheel ('99), Calkins ('05 and '07), Metcalf ( f io), 

 Hausman ('20), and Taylor ('24) maintain that they made similar 

 observations. Scheel and Calkins contend that the amoebae 

 encyst before the nucleus breaks up and Calkins holds that there 

 is a multinucleated generation which ends by sexual activity. 

 Calkins says, "The fertilized cell of Amceba (unknown at present) 

 gives rise to a young amoeboid organism formerly known as 

 Amoeba proteus." Later ('07) he sectioned the amoebae on which 

 these observations were made and maintains that he found a 

 process of internal fertilization very similar to endomyxis. 



Metcalf ('io) asserts that there are two methods of reproduc- 

 tion in which fragmentation occurs; one in which the parent 

 amoeba breaks up liberating minute amoeboid forms which devel- 

 op into large amoebae; another in which small amoeboid forms are 

 liberated from the parent by a gemmule formation. These 



1 These observations were made while the authors were working under Dr. S. O. 

 Mast, to whom they are very grateful for timely criticism and helpful suggestions. 



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