March 29, 1918] 



SCIENCE 



321 



The ability of some types to subsist on simple 

 inorganic substances (CH„ NHj and CO:) without 

 the aid of sunshine, and the sensitiveness of all 

 bacteria to the action of sunlight suggest their 

 ejristence on this planet prior to the appearance of 

 plant life or the penetration of the rays of the 

 sun through the volcanic vapors. 



We may perhaps agree that au organism 

 which can develop without organic compounds 

 of any kind, utilizing inorganic compounds 

 exclusively, would probably be primitive. 

 There is no proof, however, that the original 

 bacteria were any more sensitive to the sun's 

 rays than are plant cells in general at the pres- 

 ent day. It is not improbable that the purple 

 sulphur forms are among the most primitive 

 of our modern bacteria, and these, as is well 

 demonstrated by the work of Molisch and 

 others, grow only in the presence of light, and 

 the motile forms show a very marked positive 

 phototaxis. Most animal cells are equally 

 sensitive to sunlight with most bacteria, but 

 this does not argue that these animal cells are 

 primitive. Finally, the assvmiption that life 

 must have originated on earth while the earth 

 was still bathed in volcanic vapors, and the 

 earth's surface was dark, has little to sub- 

 stantiate it. It is quite as probable that we 

 must account for the development of life upon 

 earth on the basis of Chamberlain's accre- 

 tion theory as on the theory of a once molten 

 globe. It is not argued that either hypothesis 

 of earth origin must be accepted, but Dr. 

 Kligler's assumption is rather an insecure 

 basis for the erection of his complex super- 

 structure. 



It is rather difficult to follow Dr. Kligler's 

 reasoning through the succeeding paragraph. 

 The the.sis to be proved apparently is: "The 

 intimate dependence of both plants and ani- 

 mals on bacteria and their activities tends to 

 strengthen the conviction that these micro- 

 organisms must have preceded the others." 

 The statement may well be accurate, but the 

 examples adduced are not in all cases fortu- 

 nate. For example: "Plants can not subsist 

 without nitrates " is misleading, for many of 

 the higher plants, fungi, yeasts, alga;, etc.. 



utilize ammonia quite as well as nitrates, in 

 some cases utilizing ammonia in preference. 

 To state that in arid regions where plant life 

 is absent bacteria are also absent is simply to 

 affirm that both bacteria and higher plants re- 

 quire water for their growth, or are killed by 

 an excess of salts in the soil rather than that 

 the higher plants are dependent upon the bac- 

 teria. The author's examples of the necessity 

 of bacteria for the growth of animals are like- 

 wise not convincing as proof. 



Attention is next called to the fact that with 

 the bacteria evolutionary changes may be 

 physiological as well as morphological, and the 

 point is made that these '' adaptive modifica- 

 tions " should be traced. 



The statement that " Bacteria need only 

 minute amounts of nitrogenous food but re- 

 quire a relatively enormous quantity of 

 energy-yielding (carbon) compounds " is 

 doubtless true for many of the fermentative 

 types, but there seems to be no more reason 

 for this assertion for primitive bacteria than 

 for higher plants, or the fungi. Then it is 

 argued since most bacteria, at least the sapro- 

 phytes, can utilize nitrogen either as NH^, or 

 NO3 and show the most diverse ability to use 

 various carbohydrates, then the first path of 

 early evolution must have been increasing 

 ability to use a variety of carbohydrates, and 

 only later, when a higher scale of development 

 is reached do we find increasing power to 

 utilize complex nitrogenous comjwunds. No 

 evidence is adduced that the primitive organ- 

 isms were furnished with abundance of carbo- 

 hydrates before they had opportunity to attack 

 considerable quantities of protein or other com- 

 plex nitrogenous substances. It should be 

 emphasized that carbohydrates in the sense 

 used and in quantity needed would probably 

 be produced only by higher plants. But all 

 plants contain protoplasm, and in their decay 

 organisms have access to proteins as well as to 

 carbohydrates. In spite of the array of sup- 

 porting evidence, it seems that there is no ade- 

 quate proof that utilization of carbohydrates is 

 any more primitive a function than is proteo- 

 lysis. 



The point is made that there are four prin- 

 cipal types of primitive oxidizing bacteria, 



