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Till-: . 1 Mi: RICA X NATURALIST 



[Vol. XLIII 



of the anomaly, but by the fact already cited that normal 

 individuals of abnormal ancestry are more apt to produce 

 abnormal offspring than are normal individuals of an- 

 other strain. 



The studies of Lewis and Embleton and of Pearson on 

 the inheritance of split hand and split foot in man yield 

 results in many respects similar to the preceding. Al- 

 though the normal condition seems to be recessive, segre- 

 gation does not occur in Mendelian ratios. Often both 

 hands and both feet were abnormal, but frequently not 

 in the same way, and in many cases there were marked 

 differences in the variations on the two sides of the body. 

 As Pearson remarks, it is difficult to specify in such cases 

 what the unit character may be. With this, that or the 

 other bone present in some individuals and absent in 

 others and represented in very varying degrees of de- 

 velopment, the inheritance gives little evidence of definite 

 units of any kind. What is inherited appears to be a 

 condition which manifests itself in varying ways and de- 

 grees and which can not be accounted for by any theory 

 of the sharp segregation of characters. 



Why certain germinal variations are strongly inherited 

 and others not is a problem of much interest, but the solu- 

 tion of it may lie, not in the supposed behavior of distinct 

 morphological entities representing certain parts, but in 

 the physiological relations of the basis of the variation 

 to the organized structure of the germ plasm. The sex 

 cells are organisms as well as the bodies that arise from 

 them; they have the same capacity for self regulation; 

 and it is not at all probable that all kinds of variations 

 that may arise in response to the various influences to 

 which they are subjected should be retained to the same 

 degree. Weismann has made the suggestive comparison 

 between the variations of an organism and the oscillations 

 of a polyhedron on one of the faces upon which it rests. 

 If the oscillations are small the body tends to come to 

 rest in the same situation as before; if they are larger it 

 may topple over upon a new face about which it may oscil- 



