EXPERIMENTS ON ARTHROPODS 125 



If put under water it still makes swimming move- 

 ments, but these do not help it forward. 



The experiments on the other ganglia of this ani- 

 mal performed by Bethe do not concern us in this 

 book. We will only quote that result of Bethe's 

 which is of most importance for our purpose : " Nei- 

 ther the subcesophageal nor the prothoracic ganglion 

 is the seat of the reflex for righting the animal when 

 turned on its back, nor of the coordination of the mus- 

 cles of locomotion, walking, or swimming, as Faivre 

 maintains. It would seem as though these reflexes 

 were located rather in each thoracic ganglion for the cor- 

 responding segment" This last sentence expresses the 

 principal truth for all complicated central nervous sys- 

 tems. Each segment of a segmented animal may be 

 regarded as a simple reflex animal, comparable to the- 

 Ascidian, and the analysis of the reflexes depends 

 upon the same principles and leads to the same re- 

 sults in both cases. The complication that appears 

 in segmented animals consists in the fact that when a 

 process of stimulation takes place in one segment it 

 is communicated to the neighbouring ganglia, and 

 these ganglia produce processes of the same kind. It 

 is possible that the nature of the stimulation also 

 helps to determine the nature of the movement. The 

 assumption of special centres of coordination is 

 superfluous. One other fact is of importance in exper- 

 iments in extirpating and severing nervous connec- 

 tions, namely, that the division may bring about in 

 those parts which are protoplasmically connected with 



