122 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG 



Statistical means and, indeed, no evidence not backed by statistics can 

 be accepted, for we seem particularly liable to subjective errors when 

 temperatures are concerned. As a casual speculation, I have thought 

 that this is because we were evolved in a tropical climate and can live 

 in temperate climates only because we wear clothes and have houses, 

 so that we can maintain a tropical temperature next to our skins. We 

 are very appreciative of the rise of temperature in the spring, and have 

 a te. dency to think that animals are too. They may, however, have 

 been evolved in this climate, or even in a colder one, and so may be 

 indifferent to those low temperatures normal at the date when they 

 usually breed. It is a curiosity of the literature on this subject that the 

 same authors who consider that rising temperature is a stimulus to 

 spawning also remark on cases of the animal spawning in partly 

 frozen ponds, events that are rather difficult to reconcile with one 

 another. The matter was settled beyond reasonable doubt in the 1935 

 paper, and it is to this that attention must first be given. 



The whole of the data comes from the Phenological Reports of the 

 Royal Meteorological Society, which may be briefly described in the 

 following paragraph. 



Many years ago, this society began to collect the dates of a large 

 number of natural events, such as the first arrivals of migrant birds, 

 or the first flowering of certain plants. It was felt that plants and 

 animals integrate the effects of the weather, and act as a kind of 

 automatic indicator in which the weather and climate of an area are 

 reflected in a property known as "earliness." A large number of 

 voluntary observers collected the data on forms provided by the 

 society, and once a year these were summarized and published. In this 

 way, over the years, an enormous mass of data has accumulated. In 

 1926, late in the life of the scheme, frog-spawn was added to it and, 

 as soon as I could, I collected the data from the society, and began 

 statistical work upon it. The results were published in 1935, and some 

 of the conclusions were then so certain that they have not been re- 

 examined in the much larger scheme completed in 1958. On other 

 points, I suggested that the data available in 1935 were not enough, 

 and the matter should be allowed to rest for about thirty years. This 

 period never elapsed, for the society was unable to get support from 

 other societies and felt itself unable to carry on alone. In fact, its very 

 valuable work had gone on so long that biologists have enough 

 material for years of statistical work. 



