] TO PROTOZOA 



parable numbers of varieties restricted to each continent. On 

 the other hand, such a search might well reveal that some of the 

 varieties found so far only in North America occur also else- 

 where. Yet it is not to be assumed that we have already found 

 all the varieties on this continent. Within the past year, three 

 new small animal varieties (10, 11, and 14) have been found 

 here; we have only begun to search for the large animal varieties; 

 the far north (Canada and Alaska) has not been sampled at all; 

 and we still have some large animal strains from the United 

 States that we have not yet been able to identify or even to 

 get to mate at all. 



Without going into the quantitative details, which are given 

 in Table II for the small animal varieties, it is clear that tempera- 

 ture is a major factor influencing the range of a variety on the 

 continents where it occurs. Variety 6 has the highest temperature 

 preference, being the only variety found in the hottest collecting 



Table II. Distribution by Rough Temperature Zones of the Smaller Animal 



Varieties of Paramecium <turdia a 



" Varieties 12, 13, and 15 are the larger animal varieties; these are excluded 

 because they have been little searched for. The numbers in the body of the table 

 (except the bottom row and last, column) are the percentages of all collections 

 from a zone which belong to each variety. Cold zone: northernmost U.S.A., 

 Norway, and Scotland; cool /one: England, northern France, Germany, and a 

 strip across the U.S.A. just south of the most northern states; moderate zone: 

 hi (Honshu), southeast, Australia, Switzerland, northern Italy, and the 

 middle region of the I'.S.A. (north-central California to Virginia and the Caro- 

 linas); warm zone: southernmost U.S.A. (New Mexico to Florida), Peru, north 

 and central Chile; hot zone: Puerto Rico and southern India. 



