and Laboratory Methods. 1547 



abnormal, cramped positions for long periods of time. Movements are normal 

 in character, but spontaneous movements are again less frequent than in the 

 normal animal. The primary function of both the forebrain and the 'tweenbrain 

 is to stimulate the animal to spontaneous movement, /. e., furnishes motor 

 impulses. The olfactory lobes alone have this power to some extent. The 

 forebrain is lacking in any appreciable regulatory effect on the movements, but 

 the 'tweenbrain has, in a small degree, such an effect. Removal of the mid- 

 brain causes a pronounced increase in the activity of the animal. All directive 

 influence over the movement is lost, the animal proceeding in a straight line 

 until it is stopped by some obstacle. The co-ordination between the different 

 extremities is preserved, but the movements of the individual appendages are 

 wild and exaggerated. The chief function of the midbrain, in its relation to 

 the movement of the animal, is evidently an inhibitory and regulatory one. 

 Removal of the cerebellum has no observable effect on the animal. Turtles in 

 which the nervous system has been transected at the point of junction of the 

 medulla with the cord show only very slight spontaneous movements of single 

 appendages. There is no spontaneous locomotion. The reflex irritability of 

 the posterior part of the body is greatly increased, and various forced move- 

 ments appear. Locomotion in a straight line forward can only be induced by 

 very strong stimulation at the posterior end of the body. In this movement 

 the different appendages are fairly well co-ordinated. The most important 

 function of the medulla is the inhibition of spinal reflexes. 



Electrical or chemical stimulation of the surface of the cerebral hemispheres 

 causes no muscular movement, or tonic cramps, or convulsions, such as result 

 from similar stimulations of the mammalian brain. r. p. 



Holmes, S. J. Phototaxis in the Amphipoda. ^he author investigated the photo- 

 Amer. Jour. Physiol. 5: 211-234, 1901. ° '^ 



tactic response in about twenty species 



of aquatic and terrestrial amphipods. The aquatic Gammaridea were found to 

 be uniformly negatively phototactic. This reaction may be modified and 

 obscured by the thigmotactic reaction, but positive phototaxis does not appear 

 under any conditions. The terrestrial forms most studied were Talorchestia 

 longtcornis, Onhestia agilis, and Orchestia palustris. All three species are 

 positively phototactic under ordinary conditions, the intensity and precision of 

 the reaction in each case being correlated with the general habits of the organ- 

 ism. The positive reaction is less decided in those species which are habitually 

 exposed to the most light. Talorchestia longicor?iis always reacts positively 

 both in weak and in strong light. Nevertheless this animal generally comes to 

 rest in shaded areas, presumably because it is less stimulated in the shade. 

 The normal positive reaction of Orchestia agilis is temporarily changed to 

 negative by keeping the animals for a time in the dark. When returned to the 

 light they again react positively. A rather remarkable fact was brought out by 

 the experiments on this form, it being found that if specimens that are exhibiting 

 a well marked positive reaction in strong light, are suddenly brought into weak 

 light, their reaction becomes immediately strongly negative. This reversal is 

 independent of changes of temperature. The phototaxis of Orchestia palustris 



