THE CRITERIA OF LIVINGNESS 95 



is, Huxley said, " a Sisyphean process, in the course of which 

 the living and growing plant passes from the relative sim- 

 plicity and latent potentiality of the seed to the full epiphany 

 of a highly differentiated type, thence to fall back to sim- 

 plicity and potentiality again ". So is it also among animals. 

 The microscopic egg-cell divides and re-divides, and there is 

 built up an embryo. This may develop steadily and directly 

 into the likeness of its kind, or it may give rise to a divergent 

 larval phase such as we are familiar with in caterpillars 

 and tadpoles. Through more or less critical phases of ado- 

 lescence the adult stage is reached, and it is a not infrequent 

 achievement to lengthen out this period of full epiphany 

 and freedom. But whether the creature's life is counted 

 in days or in months, years or centuries, there is for most 

 an ascending and a descending curve from the vita minima 

 of the egg-cell (which often dies in a few hours if it be 

 not fertilised) to the vita minima of senescence or to the 

 not less frequent terminus of violent death. 



In reference to Sir Michael Foster's definition, " A living 

 thing is a vortex of chemical and molecular change ", Pro- 

 fessor Bateson points out that the living " vortex " differs 

 from all others in the fact that it can divide and throw off 

 other " vortices ", through which again matter continually 

 swirls (1913, p. 40). The parallel, he says, may be carried 

 even further, for a simple vortex, like a smoke-ring, if pro- 

 jected in a suitable way, will writhe into two rings. " If each 

 loop as it is formed could grow and then twist again to form 

 more loops, we should have a model representing several 

 of the essential features of living things" (1913, p. 40). 

 It has to be added, as we have seen, that the living vortex 

 is the seat of complex and specific chemical changes which 

 are correlated in such a way that the creature lasts. 



