402 C. H. TURNER 



started in other directions. When such larvae approached 

 the horizontal, either they fell to the bottom, or each time 

 the posterior end was raised in the process of looping, it swung 

 downward somewhat, thus producing an orientation with the 

 anterior end up. To test their reactions in water, larvae six 

 millimeters long were placed in a glass jar containing water 

 twenty centimeters deep. All of the larvae reached the bottom, 

 but there was no evidence of either swimming or orientation; 

 in many cases the longitudinal axis was nearly horizontal. 

 From these experiments, Mast concludes that blow-fly larvae 

 do not react to gravity either in the water or out of it. Accord- 

 ing to Loeb's definition of a tropism, this conclusion is sound. 

 Mclndoo " has made a careful study of Troglohyphantes 

 (Willibalda) cavernicola Keyserling and Meta memardi Latreille, 

 two spiders inhabiting the caves of Indiana. The first form, 

 which is often blind, lives in total darkness; the other form, 

 which always has eyes, lives both in total darkness and in twi- 

 light. When the light of a carbide bicycle lamp was flashed 

 upon these spiders, in the cave, the Troglohyphantes made no 

 response; but the Metas darted away into the darkness. For 

 thirty days a series of laboratory experiments to test the re- 

 sponses of these creatures to light were conducted upon speci- 

 mens enclosed in glass bottles and in glass tubes. The closed 

 end and the lower half of each such vessel was covered with 

 black carbon paper; the open end was securely closed with 

 an air-tight cork stopper. One specimen, with one or two 

 drops of water, was placed in each receptacle, which was then 

 placed on an inclined rack in a south window. These cages 

 were occasionally rotated, so as to have the light strike the 

 eyes of the spiders, and, at intervals, the dark paper was trans- 

 ferred to the cork end of the tubes. The adult Metas were 

 always found in the dark end during clear and cloudy weather, 

 and in the light end when it was dark. The spiderlings of Meta 

 remained in the dark end one-half of the time during clear 

 w^eather and one-third of the time during cloudy weather. When 

 it was dark, these spiderlings spent most of the time in the 

 light end. Twenty-six per cent, of the Troglohyphantes ex- 

 amined had no external eyes, and the remainder had eyes 

 varying from mere pigment flecks to normal eyes. It was found 



