412 H. R. HULPIEU AND D. L. HOPKINS. 



amoeboid forms he asserts develop flagella, then fuse in pairs, 

 after which the zygotes thus formed develop into large amoebae. 



Taylor gives a detailed description of the nuclear processes 

 accompanying fragmentation. She maintains that the small 

 fragments as they emerge from the parent amoeba are cysts which 

 hatch out after varying lengths of time. 



All of these observations indicate that Amceba proteus at times 

 fragments, forming numerous small amoeboid forms, and they 

 appear to indicate that these small forms develop into the large 

 forms which are usually studied. Hausman contends that he 

 actually observed the transformation. There are, however, some 

 prominent investigators, who hold that the evidence presented is 

 not conclusive; for example, Schaeffer, ('26, p. in.) who says, 

 "We find no proof that the life cycle of the common large ameba 

 includes more than . . . reproduction by fission." The follow- 

 ing observations have a definite bearing on this question : 



During the last two years we have had under close observation 

 numerous cultures of Amoeba proteus, started from a few speci- 

 mens collected in the summer of 1924. During this time it was 

 repeatedly noticed in various cultures that the amoebae multiplied 

 very rapidly for a while, then suddenly practically disappeared. 

 At first these cultures were all discarded, except a few which were 

 saved for the other protozoa living in them. These were set aside 

 and observed from time to time. After about a week, large 

 numbers of minute amoebae were found in some of them, and 

 several weeks later numerous large amoebae. 



In further observations it was discovered in several cultures ot 

 large amoebae, (i) that after a period of rapid multiplication by 

 fission the specimens became increasingly more sluggish, darker 

 and more granular in appearance ; (2) that they began to decrease 

 in number; and (3) that as the large amoebae decreased small ones 

 appeared and increased. This did not occur in all cultures, for in 

 some all amoebae died. 



This disappearance of the large amoebae was observed to occur 

 in several cultures as the solution changed from acid to alkaline in 

 reaction (pH 6.8 to 7.4) or vice versa. In other cultures, however, 

 there was no such change, in these the solution remained almost 

 constant as to bacterial content, clearness, amount of food and 

 hydrogen -ion concentration. 



