go COMPARATIVE PHYSIOLOGY OF THE BRAIN 



after being exposed to the light, the decapitated worms 

 made the first movements. The interval was about 

 the same in normal worms. 



Lnmbrici fcetidi live in the decaying compost of 

 stables, and probably the chemical nature of certain 

 substances contained in the compost holds them 

 there. When one-half of the bottom of the box is 

 covered with moist white blotting-paper, the other 

 half with a thin layer of compost, all the normal worms 

 that are placed on the paper soon gather on the com- 

 post. The aboral pieces of divided worms behave in 

 the same way. When placed upon the blotting-paper, 

 they are not attracted directly by the odours of the 

 compost, but as soon as they come in contact with it 

 in moving about, they crawl on it and do not leave it 

 again. After a short time all the brainless worms are 

 on the compost. When placed on a heap of compost, 

 most of them crawl into it within a short time. This 

 is not due solely to the light, as the same reaction 

 also takes place in the dark (2). 



Thus we see that in decapitated earthworms all the 

 reactions shown by the normal worms are retained. 

 Hence the brain (supracesophageal ganglion) has in 

 this case no leading role. 



We cannot be too careful in drawing conclusions 

 in regard to the principal function of a ganglion. 

 Nereis, a much more highly developed Annelid than 

 the earthworm, burrows in the sand ; if decapitated, 

 this function ceases. One might suspect that this was 

 due to the loss of the brain, but such is not the case. 



