400 Maternal Inheritance and Mendelism 



will, we think, be able to put forward a satisfactory explanation of this 

 phenomenon. We merely, at present, say that this appearance is not 

 really contradictory to the maternal inheritance. 



Causes of Maternal Inheritance. 



Concerning certain characteristics such as the whitish grey, spindle- 

 shaped, or yellow and white colour of newly laid eggs whose origin is 

 due to the shell or yolk which are entirely derived from the maternal 

 body, the maternal inheritance is the natural consequence, and may be 

 compared with the inheritance of certain characteristics of the seed-coat 

 of plants which are of purely maternal origin. 



Concerning the colour of the egg, whose origin is due to the special 

 pigments deposited in the serosa, the case is quite different. As the 

 serosa is formed of cells derived from the conjugation of paternal and 

 maternal nuclei, the egg-colour ought to be influenced by the paternal 

 characteristics if they are dominant, but, as we see, it is entirely maternal 

 in certain colours, such as the reddish brown, blue, normal colour, etc. 



Nothing is as yet known as to why these serosa characteristics 

 behaved as maternal in inheritance. We are now waiting the results of 

 the further series of experiments which we have been engaged upon 

 concerning this question. 



There are other characteristics of the silk-worm which behave 

 maternally in inheritance. They are the brood characters such as uni-, 

 di-, or multivoltine, or "voltinism" of the silk-worm. The fact of 

 maternal inheritance of these characteristics was first observed by me 

 (1906) and was proved by McCracken (1909), who was led to the 

 conclusion that the order of inheritance was non-Mendelian, while Castle 

 (1910), upholding the fact that they are maternal in inheritance, says 

 that univoltinism is a Mendelian dominant to divoltinism. 



Voltinism. 



McCracken's results may be compared with those obtained by us in 

 the series of experiments above referred to, but in the case of voltinism, 

 as there are many causes disturbing the proper elimination of parental 

 characteristics which are entirely neglected by her, it is rather premature 

 to consider the phenomena of inheritance displayed by the character 

 " voltinism " as non-Mendelian. We enumerate here those disturbing 

 causes : (1) divoltine character may easily be changed by the influence 



