vii THE NUCLEUS AS A NERVE-CENTRE 349 



now from one, now from another ectoderm-cell, or group of 

 such cells, and spread from thence by simple contact since 

 no nerves exist to the neighbouring cells, and so communicate 

 itself to all the muscular processes. 



Brains, or a brain, as the case may be, could only arise in 

 consequence of the fact that certain ectoderm-cells, or groups 

 of such, came- more frequently into contact with the outer 

 world, and accumulated experience, or that were from their 

 favourable position adapted to form the middle point for the 

 activities of a larger number of neighbouring cells cerebral 

 ganglia could only be developed in consequence of the 

 inheritance of acquired characters. 



THE CELL-NUCLEUS AS A CENTRAL NERVOUS ORGAN. 



But if the individual cells of the ectoderm are capable, as 

 the view I am advocating supposes, of giving rise to volun- 

 tary action, we must seek in them some apparatus which serves 

 as a central nervous organ ; and this apparatus can only be the 

 nucleus. 



Thus I am brought back to a question previously sug- 

 gested, Whether the nucleus of the unicellular organism is 

 not also to be regarded as its central nervous organ ? 



For the larval Blastula is certainly, like the Volvox colony, 

 only an aggregation of unicellular beings. And an affirma- 

 tive answer to the above question is supported by numerous 

 facts which I have already brought forward in my papers on 

 Beroe and on the Medusae. In these I have described the 

 nucleus in general as the central organ of the cell, as its organ 

 of life, in the sense that it originates and governs the pro- 

 cesses of life in the cell, while in the animal cell I have con- 

 sidered the nucleus as the central nervous organ. 



I was first led to this view by considering the great 

 importance of nuclei in every nervous system. The nucleus 



