EFFECTS OF AMPHIMIXIS ON ONTOGENY 285 



of the mother remained in the ovum from which the daughter 

 was developed, the group of idants of the other grandparent, 

 which would modify this type somewhat, must necessarily be 

 absent ; the types of the mother and daughter consequently 

 cannot exactly correspond, for the double reason that the influ- 

 ence of one grandparent was wanting at the development of the 

 daughter, while that of the father was present in addition. 



The following examples may serve to show in how inatiy 

 different ways tlie hereditary tendencies of the parents niay, in 

 accordance with our theory, be interchanged in the course of 

 ontogeny. In the bilaterally symmetrical human being, all those 

 parts which are not situated in the median line are paired, and 

 the corresponding organs generally behave nearly, if not quite, 

 similarly as regards heredity. If one hand bears a decided re- 

 semblance to that of the mother, the same will, as a rule, be 

 true of the other also : and if the left leg is intermediate be- 

 tween the character of both parents, the right one will also be 

 so in exactly the same degree. Even such a subtle characteris- 

 tic as the colour of the eyes usually corresponds in both organs ; 

 and even in those cases in which it is intermediate betw^een that 

 of the two parents, the colour only varies slightly in shade in 

 the two eyes. One might be disposed to conclude from this 

 fact that paired organs are represented by a single primarv con- 

 stituent in the germ-plasm. This, however, would be an erro- 

 neous conclusion ; for. apart from the facts already mentioned 

 which contradict such a view, there are exceptions to the ride 

 that paired orgajis are similar to one another. One brown and 

 one blue eye sometimes occur in dogs, especially in boar-hounds, 

 and I know^ of a similar instance in the human subject : the 

 father, a brewer in a small Suabian town, has blue eves, and the 

 mother brown ones, while a daughter of twelve years of age has 

 one blue and one brown eye. 



In addition to these cases, the frequent inheritance of birth- 

 marks and other minor characters on one side of the body only, 

 necessitates the assicmption of double deterininants for the cor- 

 responding parts of eachjialf of the body. We must therefore 

 imagine that each id of the germ-plasm of bilateral organisms is 

 primarily bilateral, and that all the determinants, indeed, of the 

 whole body are double, even of course including those for the 

 organs which are apparently situated in the median plane, but 

 which actually consist of corresponding halves. In a large num- 



