328 SCIENCE PROGRESS 



open and closed chain compounds is not such that chemists can 

 regard one as more primitive than the other, except it be that the 

 open is the first to receive attention in the text books ; and arginine 

 if not the most, is one of the most complex products hitherto 

 separated from albuminoid materials, far more so than tyrosine : 



Arginine HN = C< NR 2 CH CH 2 . CH 2 . CH(NH,) . COOH 

 Tyrosine HO . C 8 H 4 . CH 2 . CH(NH,) . COOH 



Arginine probably owes its value as a nuclear material to the 

 many points of attachment its nitrogen atoms offer — in other 

 words, to its complexity. 



Professor Minchin would restrict the term cell to organisms 

 in which the protoplasm is differentiated into cytoplasm and 

 nucleus definitely marked off from one another and would there- 

 fore deny the term cell to Bacteria and their allies. But Bacteria 

 apparently consist of materials differing but little in complexity 

 from those met with in higher organisms and they contain a 

 variety of enzymes. The separation of the nucleus within a 

 special differential septum would appear merely to mark it off 

 as a separate factory within which special operations can be 

 carried on apart from those effected in the cytoplasm ; the 

 extrusion of nucleoli from the nucleus during the vegetative 

 stage is particularly significant from this point of view, especially 

 as the nucleoli within and without the nucleus stain differently. 1 

 The differentiation of the nucleus therefore may be merely a 

 mark of a higher stage of organisation but to make the distinction 

 suggested between Bacteria and other forms appears to me to 

 be unjustifiable. 



From the point of view I am advocating, every organism 

 must possess some kind of nucleus — visible or invisible : some 

 formative centre around which the various templates assemble 

 that are active in directing the growth of the organism. The 

 cell, in other words, is the unit factory and its definition should 

 be made independent of microscopic appearances. 



To conclude. All speculation as to the Origin of Life must 

 savour of the academic ; it can have no very definite outcome 

 unless it be verified experimentally and at present it seems 



1 See especially " Observations on the history and possible function of the 

 nucleoli in the vegetative cells of various animals and plants." By C. E. Walker 

 and Frances M. Tozer, Quart. Journ. Exp. Physiol. 1909, 2, 187. 



