November 6, 1914] 



SCIENCE 



661 



other words of an inactive body into an active 

 one. In the second instance, there is not only 

 activation, but the extremely important addi- 

 tion of the male stereochemic system which by 

 admixture with the female system constitutes 

 a female-male system. Therefore, in the first 

 place the offspring is developed solely from the 

 female stereochemic system, and in the second 

 place from the combined female and male sys- 

 tems, one or the other of which may be wholly 

 or in part dominant in determining certain 

 peculiarities in the developmental changes. 

 Moreover, owing to the transmutability of 

 stereoisomerides and the multiphase transmu- 

 tability of stereochemic systems, coupled with 

 the reversibility of metabolic processes which 

 may be due to even the simplest of changes in 

 physico-chemical mechanisms, we have a log- 

 ical basis for the explanation of the phenomena 

 of sexual dimorphism that is expressed in the 

 so-called male and female ova, and male and 

 female spermatozoa; of primary and second- 

 ary hermaphroditism; of paradoxical sex 

 developments where the unfertilized egg 

 develops into either male or female oilspring; 

 and of sexual transmutability of the inherently 

 male or female ovule. 



It follows upon the basis of our theory that 

 because of the inherent peculiarities of the 

 stereochemic systems of the germplasms and 

 the definitely predetermined nature of the 

 entire series of reactions in accordance with 

 the laws of physical chemistry that " like be- 

 gets like " because like every other physico- 

 chemical phenomenon, individual or serial, 

 under given conditions, it is a physico-chemical 

 fatality. Edward Tyson Eeichert 



Univeesitt op Pennsylvania 



TBE CONTENT AND STBUCTUBE OF TEE 

 ATOM^ 



This lecture has presented to you a vision 

 of the recent struggle toward a better knowl- 

 edge of the atom. Both experimental results 

 and theory have been briefly discussed. You 

 can readily place confidence in the former, 



1 The closing portion of the address of the re- 

 tiring President of the Iowa Chapter of Sigma 

 Xi, delivered on October 14th. 



but in the realm of theory you are unable to 

 distinguish truth from error. I have brought 

 to you, then, not the satisfaction which one 

 enjoys in believing he hears the final truth, 

 but rather the discontent with which the 

 scholar views the limitations of knowledge in 

 his field. Such discontent gives birth to zeal- 

 ous endeavor to learn new truth and is thus 

 the precursor of that research in science which 

 our society is organized to encourage. An at- 

 tempt to think in sub-atomic terms very 

 quickly makes one conscious of the limita- 

 tions of our knowledge. But I wish to em- 

 phasize that such limitations occur in all sci- 

 ences and, indeed, at any point that a scholar 

 chooses to make his special study. These lim- 

 itations are not usually easy to extend, espe- 

 cially in the older sciences. And just such 

 difficulties furnish the challenge of scholar- 

 ship in science to the young men and young 

 women of ability. 



There is, however, no need to offer explana- 

 tions to those who are dissatisfied with a dis- 

 cussion in which truth and error can not be 

 separated. The unscientific mind possesses 

 but two compartments, one for truth and one 

 for error, and such a mind has no compart- 

 ment in which to place a discussion of the na- 

 ture and structure of an atom. The scientist, 

 however, recognizes no such compartments, 

 for absolute truth and absolute error are un- 

 known to him. After weighing the evidence 

 furnished, his decisions consist only in se- 

 lecting the degree of his confidence that is 

 merited by that evidence. 



Having given you a bird's-eye view of the 

 evidence, it may now be appropriate to pre- 

 sent a brief resume in perspective of the 

 great achievements in science which have beea 

 the subject of this lecture. We can now re- 

 gard the existence of the sub-atomic electron 

 with as much confidence as that given any 

 other experimental fact in physics. There is 

 yet a question as to whether or not the elec- 

 tron actually is our smallest unit of negative 

 electricity, but the affirmative evidence is 

 much the greater. The mass of the electron 

 can be called " apparent," with the restriction 

 that we know this to be true only to the de- 



