MORRISON 



T was recorded, not only on the following day, but for more than 

 a whole week thereafter. The crossed circles in Figure 9 repre- 

 sent the second week after that exposure with some return towards 

 the normal level, and then finally the lined circles show the return 

 to normal in the third week. Here, then, is a suggestion of an 



adaptation of T in response to a thermal stimulus, a response 



B 

 which as Scholander et al. (1950) point out is not appropriate to 



cold. But because a difference of only a degree or two in T in 



a hot climate may allow the elimination of evaporative cooling, it 



could be a very useful response to heat. 



In summary, the marsupials are a primative group which can- 

 not be characterized by a single thermoregulatory pattern. Some 

 show excellent regulation to cold while others are cold-sensitive. 

 Some have very effective regulation to heat while others have none. 

 There does seem to be some disposition towards thermal lability, 

 although not necessarily thermal inadequacy in the group. 



Chiroptera 



The Chiroptera have always been of special interest because 

 of the seasonal and daily hypothermia exhibited by those temperate 

 forms which have been studied. However, they are essentially a 

 tropical and subtropical group, so we should, perhaps, character- 

 ize the order in terms of the tropical representatives. It is in the 

 tropics that they show their greatest profusion, both in numbers 

 and in their specializations for different environmentalor behavioral 

 situations. The flying foxes, or Megachiroptera, weigh as much as 

 a kilo and are very substantial animals. In Australia we found that 

 one megachiropteran ( Pteropus) regulated its temperature very well 

 against cold, and that it had insulative properties and metabolic res- 

 ponses which were quite comparable to small temperate-zone mam- 

 mals of the same size (Morrison, 1959). We were, therefore, inter- 

 ested in Brazil last year to examine a series of the michrochirop- 

 teran fruit bats, largely from the Phyllostomidae. 



Figure 10 shows the daily cycle for one of these genera, 

 Artibeus. The cycle is substantial, but not extreme, with a range 

 of about 3 C between the mean minimum and maximum levels. 



398 



