398 W. H. TALIAFERRO 



tively geotropic animals. The presence of air or sea water, the 

 presence of direct sunlight, and the character of the surface 

 on which the snails move, all have some effect on the reactions 

 to gravity. "From the experimental results which the writer 

 has obtained, he concludes that neither the mechanical theory, 

 nor the pressure theory, nor the resistance theory is adequate 

 to explain the phenomenon of the negative geotropism of Lit- 

 torina littorea but a physiological one, that is, the statocyst or 

 statolith theory. This theory is the more likely since these 

 snails have statoliths. The writer, however, has no direct 

 evidence, at present, in favor of the statolith theory." A 

 similar conclusion (15) concerning the statolith theory is reached 

 after a study of the reactions to gravity of certain freshwater 

 snails. 



Lankester (17) gives certain arguments against the conclusion, 

 set forth by Carpenter (1874) and Heron- Allen (1915), to the 

 effect that the behavior of the Foraminifera is evidence of 

 intelligence in these organisms. 



In continuing their work on the relative efficiency of various 

 parts of the spectrum for the photic reactions of plants and 

 animals, Loeb and Wasteneys (18) give the following regions 

 of the spectrum as being the most efficient for the following 

 organisms: Eudendrium ramosum, 460-480/i/i ; Euglena viridis, 

 460-490/i/* ; Arenicola larvae, about 495/i/t; Chlamydomonas pisi- 

 formis, about 535/4/*; Balanus eburneus larvae, 560-578/a/z. These 

 results were obtained by subjecting the organisms simultaneously 

 to two beams of monochromatic light from different directions 

 and then comparing their distribution in the two beams. 



Lohner (19) has made some feeding experiments on leeches 

 by letting them attach themselves to a piece of fresh animal 

 hide which has been fastened to the end of a tube containing 

 blood. After the animals have thus attached themselves, in a 

 normal manner, the blood in the tube is removed and various 

 solutions substituted. In experimenting with the so-called four 

 types of gustatory solutions (salty, sweet, sour, and bitter) the 

 author finds that the animals show a ' detaching " or " repul- 

 sion ' reaction at the following percentage solutions: Sodium 

 chloride 7%; Cane sugar 5%; Quinine sulphate 0.08 to 0.1%; 

 Hydrochloric acid 0.09 to 0.1%; and Potash 0.08 to 0.9%. 

 No such reaction follows from pure water. 



