T. M. SONNEBORN 171 



zone. Varieties 7, 8, 10, and 14 come next. With three exceptions, 

 my strains of these varieties come from Florida; the exceptions 

 are from Mississippi (variety 14), New Mexico (variety 8), and 

 Maryland (variety 8). Variety 4 ranges from cool to warm 

 climates, but it is absent from the coldest and hottest collecting 

 sources; it is equally prevalent in moderate and warm regions, 

 rarer in cool regions. Variety 1 has been found in all zones except 

 the hottest, but its peak frequency is in the moderate zone. 

 Variety 2 has the same range as variety 1, but its frequency de- 

 creases with rising temperature. Varieties 3 and 5 have never 

 been found either in warm or hot regions; variety 3 has its peak 

 in the cold zone, variety 5 in the cool zone. Variety 9 has a dis- 

 tribution in Europe somewhat like that of variety 3 in North 

 America. 



Much less is known about the distribution of the larger animal 

 varieties. That is why they were not included in Table II. Giese's 

 (1941, 1957) survey of variety 16 is the most extensive. He 

 obtained 16 collections of this variety from various regions of the 

 United States extending from Oregon and New Hampshire in the 

 north to Texas in the south. From this it would seem that variety 

 16 has a wide temperature range. I have now four collections of 

 variety 15 from the state of Washington in the northwest to 

 Florida in the southeast. It too appears to have a wide tempera- 

 ture range similar to that of variety 16. 3 Of variety 13 I have 

 four collections, all from southern United States (New Mexico 

 and Florida), suggesting a restricted warm climate localization. 

 Only the one strain of variety 12 from Madagascar is known, but 

 no other large paramecia outside North America have been 

 examined. 



So far as present knowledge goes, it would appear that some 

 varieties, both small and large animal varieties of P. aurelia, have 

 wide temperature ranges while others — again both small and 

 large animal varieties — have narrow temperature ranges. Inde- 

 pendently of this, of the small animal varieties, some are re- 

 stricted to one continent and others are distributed around the 

 world in the appropriate temperature zones. Whether this is also 

 true of the large animal varieties remains unknown. 



