168 HEREDITY AND SELECTION IN SOCIOLOGY 



formation itself, but only a pathological and weakened organic constitu- 

 tion ; and that the teratological manifestation is the result of a congenital 

 accident which occurs during the embryonic development. The develop- 

 ment of the organs is not contemporaneous, but successive, and the localisa- 

 tion of the developmental aberrations of the organs varies according to 

 the period at which the teratogenetic influences manifest themselves. 



It may often happen that an accident to the amniotic membrane which 

 envelops the embryo affects the entire organism. Thus it is undoubted 

 that congenital influences play an important rSle as factors of teratogeny ; 

 and it is equally certain that such teratological accidents do not manifest 

 themselves except in individuals predisposed to them by a pathological 

 heredity. Consequently, Weismann's supporters might be tempted to 

 affirm boldly that the weakness inherent in the organic constitution is the 

 determining cause ahke of the malformation and of the disease. An acci- 

 dent happening during the embryonic development acts simply as a secon- 

 dary cause in the teratological formation ; and an accident, whether during 

 embryonic development or afterwards, acts simply as a secondary cause 

 in inducing the disease. Thus, the malformation is a symptom of degeneracy 

 in the constitution, just as is the disease ; the malformation being the 

 morphological manifestation of this constitutional defect, and the disease 

 its organic manifestation. This view denies the inheritance, in the scien- 

 tific sense of the word, of anything but the morbid predisposition ; the 

 teratological manifestations, as also the diseases, are due to congenital 

 or (in the case of diseases) subsequent accidents. Teratological mani- 

 festations, therefore, are not in the strict sense hereditary phenomena. 



Nevertheless, against those who maintain this view in order to escape 

 from the difficulty of admitting the transmission of purely somatic char- 

 acters, such as cranial abnormalities, etc., it may obviously be argued 

 that teratological transmission has been conclusively demonstrated in so 

 many cases that it is impossible to be content with explaining it as a mere 

 congenital accident. The question necessarily presents itself in this case : 

 If teratological malformations are hereditary, how comes it that the germ- 

 plasm is able to transmit the morphological aberrations of bodily parts ; 

 since, as we have seen, the body has no means of communicating its 

 characters to the germ ? When, for instance, an arm or a leg is amputated, 

 the result of this amputation is not transmitted, and we can readily explain 

 the fact theoretically ; for it is, on the face of it, impossible that the 

 somatic cells should be able to communicate their altered arrangements to 

 the germinal cells. There is no known mechanism by which the trans- 

 mission could be effected. Or, if it be objected that the somatic cells 

 could communicate their altered structural characters to the germ-cells 

 by means of the nervous system — as has, indeed, been alleged in support 

 of the now exploded theory of the hereditary transmission of epilepsy, 

 based on Brown-Sequard's somewhat unsatisfactory experiments — it must 



