No. 647] PROGRESSION OF LIFE IN THE SEA 487 



of light, and evolved as a last resort in failing plasma." 

 Katabolism persists as the ultimate mechanism in the 

 physiology of animal as contrasted with plant life, but if 

 the suggestion just quoted is sound, it originated, as the 

 first " adaptation " of the organism, to meet the factor 

 of recurring night and day. That the problem was suc- 

 cessfully solved we know, but as to the mechanism of its 

 solution we have no key. It is at this point again, to use 

 Church's words, that the plasma, previously within the 

 connotation of chemical proteid matter, becomes an auto- 

 trophic, increasingly self-regulated, and so far individu- 

 alized entity, to which the term ' life ' is applied." 



The elementary plasma is thus now fairly launched as 

 an individual living organism, and the great fundamental 

 problems of biology— memory, heredity, variation, adap- 

 tation—face us at each step of our further progress. We 

 see in broad outline the conditions the advancing organ- 

 ism had to meet, w^e see the means by which those condi- 

 tions were in fact met, we know that only those individuals 

 survived which were able to meet them. Further than 

 this we, the biologists of to-day, have not advanced. The 

 younger generation will pursue the quest, and, with pa- 

 tient effort, much that now lies hidden will grow clear. 



The differentiation of the growing particles of plasma 

 into definite layers, which followed, seems natural; first 

 the external layer, in molecular contact wdth the sur- 

 rounding water^ from which it receives substances from 

 outside in the form of ions, and to which it itself gives 

 off ions ; beneath this the autotrophic layer to which light 

 penetrates, and in which, under the influence of the light, 

 new organic substance is built up ; in the center a layer 

 to which light no longer penetrates. This central region, 

 the nucleus, depends entirely on the peripheral layers for 

 its own nutrition, and becomes itself concerned only with 

 katabolic processes, those processes of the or.iraiiism 

 w^liich depend upon the breaking down, and not the build- 

 ing up, of organic substance. 



At an early stage in the development of the individual 

 organism the spherical shape, which the oruanit' pl.isnia 



