476 JENNINGS— HEREDITY IN PROTOZOA. [April 24, 



Effects of Lack of Food. — From the culture shown in row 23, 

 Table XVIII., a large number of specimens were removed and placed 

 in a small watch-glass, which was allowed to stand for two days. 

 The food decreased rapidly and the animals became smaller, giving 

 the results shown in row 24, Table XVIII. The mean length had 

 decreased 10.174 per cent. ; the mean breadth 33.024 per cent. These 

 were now allowed to stand for three weeks more in the watch-glass, 

 without adding food. At the end of this time they were in the 

 extremes of starvation, and only 2,7 specimens remained of the many 

 hundreds originally present. These 37 gave the results shown in 

 row 26, Table XVIII. As compared with the original condition of 

 row 23, the mean length had decreased 30.638 per cent., the mean 

 breadth 55.886 per cent. A peculiar fact is that this starving culture 

 shows a very high coefficient of correlation between length and 

 breadth (.8018), while in our other starving cultures this has not 

 been the case (see rows 6 and 8, Table XVIIL). 



From the culture of large specimens shown in row 23 another 

 lot was removed January 30 and kept in a small watch-glass, new 

 hay infusion being added at intervals. In spite of this addition of 

 new food material, and the fact that they continued to flourish and 

 multiply, these decreased in length even more than in the starving 

 culture, the mean being 100.320. This is the smallest mean length 

 observed in any lot of the c line. The data for this lot are given in 

 row 27, Table XVIIL, and in Table LX. 



3. Summary on the Effects of Environment. 



The facts given above show that the nature of the environment 

 affects greatly the dimensions, proportions and variations of Para- 

 mecium, and that these effects are produced with great ease and 

 rapidity by such changes as are common in any culture of these 

 infusoria. Some of the more important effects may be summarized 

 as follows: 



Effect on Length. — Under the influence of varied nutritional con- 

 ditions the length varies extremely. In the line descended from the 

 individual D the mean length varied under different conditions from 

 146.108 to 202.280 microns — the difference being 38.445 per cent, of 

 the smallest mean length. In the c line the variation in mean length 



