140 



SCIENCE 



[N. S. Vol. XXVI. No. 657 



temperature of somewhere about Beekman- 

 town eo-Ordovician time, somewhere about 

 the time that the ocean had attained one 

 fifth of its present concentration. This 

 indicates that the pre-Paleozoic was prob- 

 ably not one fourth as long as later time, 

 dating the beginning when the ocean began 

 to get concentrated. 



Thus the rapidity of early evolution, to 

 which physical, astronomical and strati- 

 graphic evidence had led us, is confirmed. 



But we know that life existed all through 

 Cambrian time, and earlier yet. So while 

 Quin ton's investigations indicate certain 

 conditions of the vital circulating fluid 

 from which fresh-water and salt-water 

 vertebrates have diverged, while the more 

 vigorous land animals have retained them 

 nearly unchanged, these conditions are by 

 no means so near the beginning as one 

 might think from a casual reading of his 

 argument. It seems much more probable 

 that life began as soon as was possible, at 

 higher temperatures than 44° C. and at 

 very low concentrations. The water was 

 that leached from basic rocks, the Keewa- 

 tin schists, and was relatively richer in 

 calcium chloride, and I suspect also ferrous 

 chloride,'' and was in composition as well 

 as concentration by no means the best for 

 organic life. We may then believe that as 

 the temperature of the water decreased, 

 and the concentration increased, this change 

 was in the direction of the physiological 

 optimum, or salt solution most favorable 

 to protoplasm and cell activity. 



According to Meyer's account of the 

 stimulant effect of sodium chloride, cal- 

 cium and potassium, and the sedative effect 

 of magnesium, the early ocean, as it ac- 

 cumulated salts of sodium and lime, must 

 have been a more and more stimulating 

 medium, up to a point when it became over- 

 stimulating and poisonous. Up to this 



" Compare the richness of iron carbonates in the 

 liuronian. Probably mixed carbonates were pre- 

 cipitated as fast as carbon dioxid was furnished. 



time, which I take to be about the begin- 

 ning of the Cambrian, there would have 

 been no physiological tendency to secre- 

 tion or excretion of lime by animals, until 

 and unless the ocean became supersaturated 

 with carbonate. The ocean in the begin- 

 ning must, like fresh water to-day, have 

 acted as an active solvent if any were 

 formed. But when it passed the optimum 

 then the excretion or precipitation of lime 

 and accumulation of magnesia, which is 

 more sedative, might tend to restore the 

 balance. So long as it could thus be kept 

 in most favorable condition for cell life, 

 there would be no especial reason for 

 osmotic closing or the development of a 

 special vital fluid. Up to this point it 

 would pay animals to accept the beneficial 

 changes- which were taking place in the 

 medium in which they lived and moved and 

 had their being. 



We do not, understand, suppose that the 

 ocean arrived at the best conditions for 

 cell life in all respects at the same time, 

 but we suggest that one of the first en- 

 deavors of the more vigorous animals to 

 keep the vital medium of the best was by 

 means of secretion of superfluous lime. 

 This is supported by the fact that lime is 

 the substance most abundantly brought in 

 by rivers, one in which saturation would 

 soon be reached of the carbonate, and by 

 the fact that lime skeletons and hard parts 

 begin to be abundant in the Cambrian, a 

 geologic period before those animals ap- 

 peared which we may be sure had a sepa- 

 rate vital fluid. However, our general be- 

 lief in the critical importance in the history 

 of life of the time when the ocean passed 

 through the most favorable conditions for 

 cell life does not depend on any particular 

 theory of the physiological interrelation of 

 various salts.' 



' But we do suggest that the secretion of hard 

 parts began first as a physiological reaction, like 

 renal calculi, to the increasing hardness of the 

 vital medium. 



