122 SCIENCE PROGRESS. 



Wilson aright, his proposed modification of the so-called 

 mosaic theory does, in some measure, justify the use of the 

 term, since emergence of the mosaic-like character of the 

 ontogeny from the indifferent condition of the early stages 

 is due to the action of an external factor, viz., the embryo- 

 logical development. This, at least, is one interpretation 

 which might be put on his somewhat obscure reasoning. 

 But I am not sure that he does intend to say this, but 

 contrariwise, that the mosaic character is dependent on 

 the internal factor, viz., the nature of the idioplasm of the 

 ovum. In this case, the use of the word mosaic is not 

 only misleading, but mischievous. 



The mosaic of Roux (and of Wilson ?) determines its 

 own pattern ; the organism, according to Whitman, domi- 

 nates its own development, not because of cellular inter- 

 action, that is denied, but because of some intrinsic 

 property, an organisation which precedes cell formation 

 and regulates it. Now the pattern of a mosaic is not deter- 

 mined by the forces residing within its component parts, 

 nor is it conceivable that the organism, that is the final 

 aggregate of parts which have been successively formed, 

 dominates the formation of parts without which it has no 

 existence. There is a fallacy here in the word organism. 

 Whitman is the last who has spoken on this subject, 

 evolution or epigenesis, and his attempts to find an 

 explanation of vital phenomena, to discover some ultimate 

 cause of observed sequences, are hardly more satisfactory 

 than the attempts of those who have preceded him. He 

 seems himself to be aware of this, for he ends by pointing 

 out the difficulties without offering any solution. But his 

 attempt to clear the path by breaking down the cell theory 

 will meet with very little sympathy. He appears through- 

 out his essay to be labouring under a grave misconception 

 as to the nature of the cell theory as it has been accepted 

 for many years past. He quotes the original dicta of 

 Schleiden and Schwann, and proceeds to the easy task of 

 demolishing them. As a matter of fact the cell theory as 

 originally propounded by Schleiden and Schwann has 

 undergone no inconsiderable modifications ; their very con- 



