Again, it is generally believed by embryologists that 

 physical defects or errors of development are due to intra- 

 embryonal causes, and that most of them occur in the first 

 two or three weeks. ' ' Maternal impressions, ' ' on the other 

 hand, are in the great majority of cases referred to a period 

 after the fourth or fifth month. Usually explanations are 

 found after the events, and these are put in the place of 

 causation instead of coincidence. 



While there is little or no scientific evidence in support 

 of the theory of maternal impressions as usually under- 

 stood, it is scientifically correct to assume that the prenatal 

 condition of the mother may have an indirect influence on 

 the health of the child. Beside abnormal nutrition, hered- 

 ity, however, is largely responsible for the transmission of 

 peculiarities to the child. ^" A knowledge of the pedigree of 

 Laban's cattle would undoubtedly explain where the stripes 

 came from." 



Weismann went too far, we believe, when he tried to 

 show the impossibility of the inheritance of acquired char- 

 acters. The soma plasm and the germ plasm are not au- 

 tonomous, physiologically at any rate. Recent studies go to 

 show that hormones, chalones, or internal secretions of cer- 

 tain glandular bodies and tissues in animals play an impor- 

 tant part in growth. The secretions of the so-called duct- 

 less glands, thyroid, pituitary, supra-renal, and spleen, and 

 of the interstitial tissues of the testes and ovaries, when 

 liberated into the blood, are carried to various parts of the 

 body and influence their growth. Some of the hormones 

 appear to link up the activities of the somatic with the 

 germinal substances (See Parker, Biology and Social 

 Problems). 



MacDougal injected dilute solutions of zinc sulphate 

 and other substances into the ovaries of Raimannia im- 

 mediately before fertilization. The seeds that set pro- 

 duced plants different from the mother plant, and the dif- 

 ference was transmitted to succeeding generations. 



Parallel Induction. — Many cases might be cited where 

 both the germ plasm and the soma plasm are affected at 

 the same time by an external stimulus. Prof. Gage fed 

 poultry with the aniline dye Sudan III with the result that 

 the dye not only appeared in the fat tissues but also in the 

 eggs and in the fat tissues of the chicks. Sitkowski fed the 

 larvae of the clothes moth with the same dye, and the moths 

 laid colored eggs which produced larvae tinged with the dye . 



These are examples of parallel induction. 



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