June 8, 1900.] 



SCIENCE. 



891 



in reproduction ? Let us consider what 

 this question means in the light of the pre- 

 ceding discussion. Acquired characters are 

 features which arise in the zj'gote in re- 

 sponse to external stimuli. Now the zy- 

 gote at its first establishment has none of 

 the characters which are subsequently ac- 

 quired. All it has is the power of acquir- 

 ing them. Clearlj', then, acquired charac- 

 ters are not transmitted. The power of 

 producing them is all that can be trans- 

 mitted ; and this power resides in the re- 

 productive organs and in the gametes to 

 which the reproductive organs give rise, so 

 that the question must be put in another 

 form. Is it possible by submitting an or- 

 ganism to a certain set of conditions, and 

 thus causing it to acquire certain charac- 

 ters, so to modify -its reproductive organs 

 that the same characters will appear in its 

 offspring as the result of the application of 

 a diiferent and simpler stimulus ? 



For instance, the power of reading con- 

 ferred by education, the hardness of the 

 hands and increased size of the muscles 

 produced by manual labor : is it possible 

 that these characters, now produced by 

 complex external stimuli applied at a par- 

 ticular period of life, should ever in future 

 ages be produced by the simpler stimuli 

 found within the uterus, so that a man may 

 be born able to read or write, or with hands 

 horny and hard like those of a navvy ? 



In trying to find an answer to this ques- 

 tion let us first of all look into the proba- 

 bilities of the case, to see if we can relate 

 the question to any other class of phenom- 

 ena about which we have, or think we 

 have, definite knowledge. 



When an organism is affected by external 

 agents the action may apply to the whole 

 organization or principally to one organ. 

 Let us take a case in which one organ only 

 appears to be affected, e. cj. , the enlargement 

 by exercise of the right arm of a man. Now, 

 although in this case it is only the muscles 



of the arm which appear at first sight to be 

 affected, we must not forget that the organs 

 of the body are correlated with one another, 

 and an alteration of one will produce an 

 alteration in others. By exercise of the 

 right arm the muscles of that arm are ob- 

 viously enlarged, but other changes not so 

 obvious must also have taken place. The 

 bones to which the muscles are attached 

 will be altered ; the blood-vessels supplying 

 the muscles will be enlarged, and the nerves 

 which act upon the muscles, and probably 

 the part of the central nervous system 

 from which they proceed, will also be al- 

 tered. These are some of the more obvi- 

 ous correlated changes which will have oc- 

 curred ; no doubt there will have been 

 others — indeed it is not perhaps too much 

 to say that all the organs of the body will 

 have reacted to the enlargement of the arm 

 — but the effect on organs not in functional 

 correlation with the muscles of the right 

 arm will be imperceptible, and may be neg- 

 lected. Thus the color of the hair, the 

 length and character of the alimentary 

 canal, size of the leg muscles, the renal or- 

 gans, etc., will not show appreciable altera- 

 tion. Above all, the other arm will not be 

 affected, or if it is affected the alteration 

 will be so slight as not to be noticeable. 

 Now, we know that homologous parts, 

 whether symmetrically homologous or seri- 

 ally so, are in some kind of close connec- 

 tion. For instance, when one member of 

 an homologous series varies, it is commonly 

 found that other members of the same 

 series will also vary. Yet in spite of this 

 connection which exists between the right 

 and left arms and between the right arm 

 and right leg there is no similar alter- 

 ation either in the left arm or in the 

 right leg. Now, if parts which from 

 these facts we may suppose to be in some 

 connection are not affected, how can we ex- 

 pect the reproductive organs not only to be 

 modified, but also to be so modified that 



