LIFE-HISTORY OF AMCEBA PROTEUS. 413 



Similar results were obtained in cultures on hollow ground 

 slides. All of these cultures consisted of a few drops of filtered 

 culture fluid. One large amoeba was put into each of about halt 

 of them, and none in the rest. Numerous small amoeboid forms 

 appeared in many of the former but in none of the latter. A 

 description of a typical experiment follows: 



A large sluggish individual was selected, washed three times 

 in about 5 cc. of distilled water and placed on a hollow ground 

 slide in culture fluid which had been passed through number 50 

 filter paper. This solution contained no amoebae that could be 

 seen under a highpower dissecting binocular, or a 1.9 mm. water- 

 immersion objective. The amoeba was observed from time to 

 time. The second day after it had been put into the culture fluid 

 on the slide, it became extremely sluggish and remained so. 

 The following morning it had disappeared and in the region where 

 it had been, there were from 150 to 200 minute amoeboid forms, 

 about IOM in length. A drop of fresh sterile hay infusion was 

 now added every other day for about a week and it could clearly 

 be seen that the small amoeboid forms were becoming distinctly 

 larger. Unfortunately, at the end of this time too much solution 

 was added and the forms died. 



Following these experiments several amoeba? were isolated and 

 closely watched for a long period of time. The process of frag- 

 mentation was actually observed to occur in a number of cases. 



The results obtained seem to prove conclusively that Amoeba 

 proteus at times breaks up into small amoeboid forms but they do 

 not prove that these small forms develop into large ones. The 

 evidence presented in the following paragraphs appears, however, 

 to prove this. 



On February 19, 1925, two grams of timothy hay were added 

 to 1000 cc. ot spring water and boiled for ten minutes. While still 

 hot some of the fluid was poured into a sterile 100 cc. pyrex flask. 

 This was then plugged tightly with cotton. When the flask had 

 cooled a few drops of old culture fluid, which had been passed 

 through number 50 filter paper, were added. The flask was then 

 again plugged with cotton and allowed to stand for a week. Then 

 this culture, free from amoebae as shown by careful observation, 

 was inoculated bv one amoeba which had been washed in several 



