An Introduction to a Biology 



Mendelians, says Dr. Keid, have lately suggested that the 

 inheritance of sexual characters may be Mendelian. We 

 shall be much nearer the truth, he thinks, if we say that 

 the inheritance of Mendelian characters is sexual. 



There is undoubtedly a parallel between the manner in 

 which Mendelian and that in which sexual characters are 

 inherited. The Mendelian view is that Mendel's work has 

 provided us with conceptions which will enable us to account 

 for the mass of hereditary phenomena ; the latest extension 

 of the method being an attempt to account for the pheno- 

 mena of the inheritance even of sex by it. Dr. Reid's view 

 is that Mendelian phenomena are merely anomalies which 

 are the result of the accidental association of certain varietal 

 characters with a mode of inheritance primarily evolved to 

 ensure bisexuality. This view may or may not be right ; 

 but it deserves careful consideration because one of the 

 most deep-rooted weaknesses of the mind is the tendency 

 to regard that with which we have been acquainted for 

 the longest time as the starting-point from which we must 

 proceed to other things. For example, the most hopeless 

 confusion characterised the attempts that were made to 

 homologise the body cavities in leeches so long as zoologists 

 persisted in regarding the coelom of that member of the 

 Hirudinea with which they had been longest acquainted 

 the medicinal leech as their starting-point, and in inter- 

 preting the state of affairs in other leeches in terms of this 

 one. And the question remained in darkness until a few 

 years ago, when Asajiro Oka showed that the coelom of the 

 medicinal leech, far from being the starting-point, formed 

 the very last term of a series of gradual modifications of the 

 body cavity ; and, in fact, that the anatomy of this leech 

 could not be understood without a knowledge of the series 

 of which it was the culmination. 



References to recent literature on this subject will be found 

 in a paper by me entitled, "On the Difference between Physio- 

 logical and Statistical Laws of Heredity " (vide supra, p. 167). 



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