Rates of Growth of Individuals 29 



Frontonia. In Frontonia, PopofT ('08) measured 

 the increase of size at two different temperatures, 14° 

 and 25°. At the lower temperature a period six times 

 as long was required to double the volume and to bring 

 on fission, as at the higher temperature. The results 

 are shown in figure 13. Each point represents only one 

 individual measured, and the dashed curves are merely 

 the simplest ones that fit the data. So far as the shapes 

 of the curves are justified by the individual data, it 

 would appear that only at 14° was there faster growth 

 at first and slower growth later. At 25°, where the 

 data were more numerous, growth in volume pro- 

 ceeded, as far as any conclusion can be drawn, at a 

 uniform rate throughout. A single clone was not used 

 for these measurements, but each growing individual 

 was compared in volume with its own sister individual 

 killed immediately after completing fission. 



Ameba. In the soil rhizopod Hartmanella hyalina, 

 a few measurements of growth rate were made by 

 Cutler and Crump ('27). They traced the shadow- 

 areas of the amebae at successive periods, the area at 

 each period being based upon ten rapidly-made draw- 

 ings. They assumed that the mean thicknesses of the 

 amebae were uniform, and the body volumes therefore 

 proportional to the shadow-areas. In the fed individ- 

 ual of figure 14, the percentage increment of volume 

 was approximately uniform over the entire period of 

 25 hours. In three other protocols it seems that 

 growth was relatively slow over the first part of the 

 observations; but the observations did not start at the 

 time of fission of the amebae. 



Plasmodium. The growth of a parasitic species was 

 studied by Hartman ('27). It was discovered by Talia- 

 ferro ('25) that when Plasmodium cathemerium was 

 cultivated in the blood of a living canary-bird, asexual 

 sporulation occurred once every 24 hours, and at 



