690 



SCIENCE 



[Vol. LV,.No. 1435 



Since 1895, a number of investigators have 

 suggested that the influence of specific internal 

 secretions might easily be used for the explana- 

 tion of the inheritance of acquired characters. 

 Last year, an English evolutionist published a 

 volume on "Hormones and Heredity" and sug- 

 gested that environmental influences influencing 

 an organ, or part, of the mother may set free 

 chemical substances (hormones) that, carried 

 through the blood to the ovaries, may affect 

 the ova in such a "way as to lead to similar 

 changes in the same organ, or part, of the off- 

 spring. By such a mechanism he would attempt 

 to account for a progressive evolution in the 

 animal series. His theory would seem prac- 

 tically to be a modfiication of the pangenesis 

 theory of Darwin with the substitution of 

 "hormones" for Darwin's "gemmules." 



Many physicians, too, have leaned toward 

 Lamarekian or neo-Lamarckian theories that 

 assume the inheritance of acquired characters 

 and some of these have suggested that in such 

 inheritance the incretions must be concerned. 

 Those who have been trained in the methods of 

 modern biology, however, usually reject La- 

 marckism, and attempt to explain the apparent 

 inheritance of "acquired characters" for a gen- 

 eration or two by assuming either a "germinal 

 injury" (in the sense of Forel's "blastoph- 

 thoria") or a "parallel induction." 



The consensus of biological opinion in. this 

 country is strongly opposed to the inheritance 

 of acquired characters. Mendelian studies lend 

 no support to the view that conditional influ- 

 ences can affect inheritance factors. Mendelism 

 is, however, difficult if not impossible to ajpply 

 to man. As some one has put it, "the propa- 

 gation of man consists of a continual crossing 

 of polyhybrid heterozygote bastards," not 

 susceptible to analysis by Mendelian methods 

 such as can be applied to the study of the 

 propagation of plants and experimental ani- 

 mals. But if inheritance of acquired characters 

 really occurred, why should there not be, as 

 Conklin emphasizes, an abundance of positive 

 evidence to prove it? When one plant or 

 animal is grafted on another, there is no evi- 

 dence that the influence of the stock changes 

 the constitution of the graft. When an ovary 

 is transplanted, the foster mother does not 



affect the hereditary potencies of the ova. 

 Until more proof has been brought than has 

 hitherto been advanced, we shall not be justi- 

 fled, so far as I can see, in accepting the 

 theory that conditional influences change 

 hereditary factors. There are, moreover, aside 

 from the problem of the inheritance of acquired 

 characters, enough relationships of the endo- 

 crine organs to heredity and development to 

 long keep us rewardingly occupied. 



CONCLUSION 



Let me summarize in a few words the situa- 

 tion as I see it. The endocrine organs are of 

 the greatest importance in normal development, 

 their incretions exerting profound formative 

 and correlative influences. In pathological de- 

 velopment, the abnormal plenotypes that ap- 

 pear often point decisively to partial anomalies 

 of constitution involving especially the duct- 

 less glands and their functions. Whether or 

 not under normal or pathological conditions, 

 hormones arising in the soma can so change 

 the ^erm plasm of ova or sperm-cells as to ac- 

 count for certain mutations or for germ-cell 

 injury is a question that deserves considera- 

 tion and merits experimental test. Finally, the 

 conjecture that conditional influences upon the 

 soma can through hormonal production and 

 transportation to parental gametes so modify 

 the geiTQ-plasm as to result in the inheritance 

 of the conditioned modification seems, as yet, 

 to have but little, if any, evidence to support it. 



Lewellts F. Barker 

 Baltimoke, Md. 



AN ANALYSIS OF STUDENT 



GRADES AT WASHINGTON 



UNIVERSITY SCHOOL 



OF MEDICINE 



This work was undertaken with the idea of 

 obtaining some definite data upon which to 

 base opinions of students' grades during their 

 medical course. As the data obtained were of 

 great interest to the staff of this school it was 

 thought advisable to publish them in order that 

 they might be used for comparison with those 

 of other schools. 



The records of those students in the classes 

 of 1914, '15, '17, '19, '20 and '21 who spent all 



