VICTOR E. SHELFORD. 



ai es, the lower third of each tube was filled with paraffin upon which sand was 

 *-.f t ( 'd while the paraffin was still warm. From each of the tubes the air passed to an 

 atinometer chamber, as previously described, so that the evaporation could be re- 

 corded while the animals were being observed. 



In order to vary dryness only, it was necessary that the flows of the three kinds 

 of air be the same. The flows were measured by collecting the air for a period of 

 five seconds in a jar filled and inverted in a vessel of water. The pump commonly 

 delivered air under sufficient pressure to force it through the filters and give a flow 

 of from 12 to 1 6 liters per minute, an amount sufficient to change the air in the 

 part of the cage immediately in front of each introducer (when all are flowing, in 

 the entire cage) in a maximum of .6 of a second. 



It was possible to adjust the flows so that they were essentially alike, without 

 collecting the gas. The boundaries of the rear walls of the cages were of solid 

 metal and the slit was midway between top and bottom. A small triangle of thin 

 paper 2 to 3 cm. long and about i cm. across the base was taken between the thumb 

 and fore-finger by the point. With the hand held firmly by resting against the 

 cage, the paper was placed in a position such that it was entirely in contact with 

 the upper half of the rear wall without bending. The piece of paper was then 

 lowered so that the broad end came in front of the slit and the deflection of the 

 paper was noted and the flows adjusted until each gave the same deflection. The 

 maximum flow was barely sufficient for effective experiments. 



The atmometers were those furnished by the Plant World. Three were selected 

 with the standard .75 and restandardized by the careful adjusting of the flows 

 until they were exactly alike. The evaporation was recorded for standard lengths 

 of time when the flows of the medium and dry air were turned alternately over each 

 of the atmometers for several periods of ten minutes and one period of an hour. 

 It was found that the evaporation of one kind of air was the same no matter which 

 evaporimeter was used. At the end of the experiments, the atinometer used with 

 the wet air showed smaller evaporation due in part to sand that was accidentally 

 blown out of the observation tube onto the atmometer. 



III. MATERIAL. 



The following species were studied: the yellow-margined 

 millipede (Fontaria corrugate Wood), ground beetles (two species 

 of Pterostichus) , the wood frog (Rana sylvatica LeC.), the red- 

 backed salamander (Plethodon cinereus Green), the sticky sala- 

 mander (Plethodon glutinosus Green) and several species of snails, 

 all from moist forest situations, maximum evaporation is about 

 11.5 c.c. per day near the surface of the ground ; the common toad 

 (Bufo lentiginosus Shaw), the digger wasp (Microbembex mono- 

 don ta Say), the bronze tiger beetle (Cicindela scutellaris lecontei 

 Hald.), the spiders (Geolycosa wrightii Em. and pikei Marx), all 

 from dry sand ridges covered with cottonwoods and pines, a 

 type of situation where the maximum evaporation per day is 

 about 32.5 c.c. The animals were kept in the laboratory under 



