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 



