Suggestions From the Study of the 



Central Nervous Systems of 



Invertabrates 



WIILIAM A. llll.roN 



For the last few years I have been studying the central nervous 

 systems of a large number of simple animals with a number of 

 objects in view. I wish to learn as much as possible about the 

 mechanism of the nervous system, not alone for individual and sim- 

 ple forms, but in general as applied to all groups. The problems of 

 how and where impulses are carried have been among the most 

 interesting. The structures which serve, connect and correlate 

 senses, movements and activities have to me been more interesting 

 than the activities themselves. What all nerve cells with their 

 processes ha\e in common and what differences there are between 

 them have been constantly in mind. The functions of various parts 

 of the neurones and the relations that cells bear to each other are 

 important considerations. How far the relationships of species 

 and groups are carried into the structure of the ganglia and how 

 far adapatations have had their influence are questions not easily 

 answered. With invertebrates as with vertebrates the problems 

 of functional divisions of the ner\ous system are subjects for inves- 

 tigation. Then there ha\e been the correlations of behavior with 

 structure, not alone in the adult, but also at various stages of 

 development. 



Perhaps the dominant thought which has been in mind so far 

 as anatomical studies go, is the question of relationship of cells to 

 each other, of fibers and tibils to each other and to cells. Are 

 neurones related to neurones in continuous and definite chains, such 

 as are clearly indicated by many Golgi, Methylen Blue and other 

 methods, or are the well known suggestions and conclusions of 

 Apathy that fibrils pass from cell to cell the correct interpretations? 

 It seems that this is a problem of great importance which has not 

 as yet reached a satisfactory solution. Different methods give 

 different results. 



