BEHAVIOR OF LOWER INVERTEBRATES 391 



of compensatory muscular movement, initiated as a relief from 

 the continued contraction of the muscles already involved in 

 turning." 



Chidester (6) gives a general account of previous work on the 

 biology of the crayfish (with bibliography), and original obser- 

 vations on feeding, reactions to light, and behavior of young. 

 Crayfish are positively phototactic in weak and negative in 

 strong light. They are most active at night. 



Clementi (7) has studied the effect of cutting the nervous 

 cord and of removing parts of the central nervous system upon 

 the movements of Julus. Merely cutting the ventral nerve cord 

 does not destroy coordinated movements of locomotion; the 

 wave-like movements ol coordinated action 01 the legs pass over 

 the region of the severed cord much as they do in a normal 

 animal. Removal of the three anterior segmental ganglia of 

 the ventral cord profoundly affects the coordination of the loco- 

 motoi appendages, and destroys the possibility ot performing 

 certain reactions. 



In the course of his extensive monograph on the Aeinetas, 

 Collin (8) gives a general account of the behavior of these organ- 

 isms and discusses the mechanism of their movements. 



Embody (9) has studied the distribution, food habits, mating 

 behavior and general activities of several fresh water amphipods. 



Ewald (10) finds that the larvae of Balanus perforatus are 

 affected by sudden changes in the intensity of light. " Increase 

 of illumination causes inhibition of locomotion, preceded by a 

 slight acceleration ; the result is a sinking. Decrease of illumin- 

 ation causes acceleration of locomotion." Green and yellow- 

 green light are the most potent in evoking these reactions as 

 well as in effecting orientations. 



Increase of temperature tends to produce a negative reaction 

 while decrease of temperature has the reverse effect. A sodium 

 chloride solution isotonic with sea water, makes negative animals 

 positive. Potassium chloride has a similar but weaker effect, 

 while an isotonic calcium chloride solution causes the larvae to 

 swim about without regard to the light. Magnesium acts as an 

 antagonist to sodium. If MgCl 2 is added to a pure Na CI solu- 

 tion it tends to evoke a negative reaction. The hydrates of 

 ammonia and sodium produce a negative reaction, while HC1, 

 H 2 S0 4 and HN0 3 have the reverse effect; acetic acid and C0 2 



