2/0 G. T. CALDWELL. 



tissue fluids. Since the present results are based on physiological 

 determinations, they are hardly comparable with results from 

 behavior studies, however, it seems reasonable to suppose that if 

 this were the entire cause of the stimulation, the increased irrita- 

 bility would continue, with additional losses of water, to a point 

 nearer the vital limit of desiccation than has been found in the 

 present experiments. Also, Shelford refers to irritability as 

 evidenced by the activity of the animals, while these experiments 

 show that the increased metabolic activity continues long after 

 the animals become inactive. To cite a special case, the meal 

 worms were active for the first 6 to 10 hours in the desiccator but 

 the respiratory rate increased for more than 60 hours. 



Since meal worms with a water loss of less than I per cent, of 

 the body weight gave an increase in respiratory rate of more than 

 10 per cent., increased concentration of body fluids could hardly 

 be the principal factor in causing the increase and suggests that 

 this is, in part, a function of the nervous system. The truth of 

 this assumption is open to investigation and further work will be 

 done along this line. 



There is a rough correlation between the highest respiratory 

 rates and the vital limits of desiccation. According to Hall 

 (1922), the vital limit of the frog is 41 per cent, and that of the 

 salamander 47 per cent. The highest respiratory rate of the 

 frog, from an average of four experiments, corresponded to 13.66 

 per cent, loss of body weight and with the salamander to 21.87 

 per cent, loss of body weight. The xerophilous animals gave up 

 water very slowly and in proportion to water losses were stimu- 

 lated more than the hygrophilous animals. 



The decrease in carbon dioxide elimination with further 

 desiccation is even more difficult to explain. No literature on 

 studies pertaining to either starvation or desiccation of the larvae 

 of Tenebrio and Alypia has been found, but Hill (1911) showed 

 that the heat production of the frog decreased with starvation and 

 Child (1919), Hyman (1919) and Allen (1919) who worked with 

 Planaria, and Bodine (1921) with grasshoppers, all pointed out 

 that starvation decreased the rate of carbon dioxide production. 

 The results from the meal worm experiments indicate a stimu- 

 lation from desiccation until the depression of food starvation 

 became a greater factor. Particularly, since the respiratory 



