72 re;ports on inve;stigations and projects. 



Mr, Breitenbecker's care. The proportion of water in the bodies of insects 

 depends very largely upon the moisture-content of the medium in which they 

 are found. The proportion of water held in the body, or the water-balance, 

 is correlated with various activities, and the lowering of this balance, or 

 surplus, inhibits several functions or processes, and is also followed by re- 

 versed response to various external agencies which may exert a stimulatory 

 action. Reproduction ensues during the stage of highest water-content. 



Many of these forms show great localization in their distribution in the 

 desert, and the ruling feature of the environmental complex, whether it 

 entails a habitat in trees, among rocks, or in the soil, is that of moisture- 

 content, which determines the behavior of the animals present. 



The animal organisms of the desert show but few external characteristic 

 xerophilous characters, but they display a very remarkable degree of coinci- 

 dence of the cycle of activity and reproduction with the rainy season and 

 their cycle of dormancy with the drier season, regardless of any apparent 

 structural adaptations. 



The Climatic Factor, by EUsivorth Huntington. 



During the past year the investigations of Prof. Ellsworth Huntington 

 have been prosecuted along three lines: (i) a study of possible changes of 

 climate in regions not hitherto investigated in this regard; (2) a further 

 attempt at a mathematical measurement of any changes which may have 

 occurred; (3) an inquiry into the possible relation of such changes to other 

 types of phenomena, both physical and human. 



In pursuance of the first line of research, a journey was made to Mexico 

 and Yucatan during March and April. It was there found that even in the 

 far south, well within the torrid zone, the alluvial terraces of mountain 

 valleys and the strands of old lakes present evidences of climatic changes as 

 marked as those of other arid parts of the world, whether in America or the 

 eastern hemisphere. Moreover, traces of ancient cultures buried beneath 

 alluvium, on the one hand, and the historic accounts of the Spanish Conquest 

 and of the times immediately preceding it, on the other hand, indicate dis- 

 tinctly changeable conditions of water-supply. In moister portions of the 

 tropics, such as central Yucatan, ruins in the midst of dense tropical forests 

 appear to indicate that when Arizona and regions in similar latitudes were 

 moister than now, those which lie farther south on the border of the zone of 

 equatorial rains were drier than at present. Thus it appears that while 

 climatic pulsations may be accompanied or occasioned by changes in the 

 general temperature of the world as a whole, and by a general increase or 

 decrease of precipitation, they are more strongly characterized by variations 

 in the activity of the aerial circulation ; that is, certain epochs are apparently 

 marked by strong winds and hence an equatorward shifting of the more 

 northerly climatic zones in winter, while other epochs are marked by weak 

 winds, slight movements of the climatic zones, and relative uniformity of 

 the seasons. 



