194 



AGGREGATION, COMPETITION AND CYCLES 



bers, which is in interesting agreement with the sunspot interval, es- 

 pecially when the various discrepancies in the data and the lack of 

 synchrony in different regions are taken into account. If, as seems 

 most probable, maxima are caused by a favorable conjunction of 

 temperature, rainfall, and food supply, a correlation must first be 

 sought with these, since they are rarely uniform over a continent and 

 frequently not through a major region at any particular time in the 

 sunspot cycle. 



TABLE 4 



Years of Maximum Animal Numbers in Relation to Dates of Sunspot 



Minima (m) and Maxima (M) 



Figures in the table are the last two figures of the year with apostrophe omitted. 



Irregular columns emphasize lack of agreement. 



TABLE 5 



Number of Years between Successive Sunspot 



Minima and Animal Maxima 



Beginning with 1933, Elton has each year brought together the 

 results of the Canadian snowshoe rabbit inquiry. This is the most ex- 

 tensive study of animal cycles to date and is to be continued through a 

 10-year interval. The results are summarized for the fourth year, 

 as well as for the 4-year period: "Altogether 673 reports were 



