378 W. H. TALIAFERRO 



are important factors in the heat resistance of P. caudatum, 

 and that such properties will predetermine whether a given salt 

 solution will have a favorable or unfavorable effect." In gen- 

 eral he finds that there is no decided effect on heat resisting 

 powers produced by continued exposure to moderately high 

 temperatures. 



Hyde and Spreier (18) find that light has a stimulating effect 

 on the reproductive power of Voriicella up to a certain optimum, 

 and that the yellow and green rays are more effective than the 

 red or blue. 



Jordan (19) gives some observations on the movements, etc., 

 of Mactra inflata while burying itself in the sand. 



In a popular paper Kanda (20) briefly considers reactions to 

 gravity " in animals from the unicellular organism to man " 

 and concludes that the behavior of all of these points to the 

 truth of the statocyst theory as opposed to the mechanical, 

 pressure, or resistance theories. 



Kellogg (21) gives a very thorough description of the ciliary 

 mechanism of a large number of Lamellibranchs. In discussing 

 the action of these mechanisms in food collection and the re- 

 moval of the material not used as food the author concludes, 

 " Volume alone determines whether the collected foreign matter 

 that reaches the palps shall proceed to the mouth or shall be sent 

 from the body on outgoing tracts." For this reason a lamelli- 

 branch can feed only in comparatively clear water and not in 

 the presence of a large amount of suspended matter. (With 

 the exception of the genus Macoma). 



According to Kepner and Rich (22) the proboscis of Planaria 

 possesses an instinct to ingest objects and the control of this in- 

 stinct lies not in the dorsal ganglia, " but in a region of the body 

 anterior to and quite near the base of the proboscis." 



In a note Kepner and Taliaferro (23) find that the natural 

 habitat is an important factor in the physiological tone of Rhab- 

 docoeles when kept under laboratory conditions and hence is a 

 determining factor in their reactions. 



Kiihn (24) has made a study of the resting condition during 

 hibernation of the snail Helix. 



Loeb and Wasteneys (25) in a study of the relative effect of 

 various parts of the spectrum for the orienting reactions of the 

 sessile hydroid Eudendrium find that the most effective region 



