ORGANIC SYMMETRY IN ARMADILLO QUADRUPLETS. 1 97 



environmental inequality except that of nourishment, and differ- 

 ences in nourishment so great as to strikingly affect the size of 

 the individuals do not at all affect the inheritance of anomalies. 

 This could be readily shown by a comparison of sets that show 

 marked size inequality with sets that show size identity. 



If then the agency at the basis of irregular distribution of 

 anomaly factors is not environmental, it must be some sort of 

 internal agency. I have been unable to think of any mechanism 

 engaged in either regular or irregular distribution of inheritance 

 factors except the obvious mechanism of mitotic cell division. If 

 this mechanism worked in .a perfectly accurate and equitable 

 fashion there would be no opportunity for any irregularities in 

 the distribution of differentiating factors; but there are irregul- 

 arities and hence the mechanism must lack accuracy. 



If the factor or factors for anomalies are present in the 

 oosperm, as we are forced to believe, they must have their seat 

 either in the nucleus or in the cytoplasm. Since the anomalies are 

 evidently as strongly inherited from the father as from the 

 mother, it is hardly likely that the locus of the factors is cyto- 

 plasmic, for the male cell has an insignificant cytoplasmic organ- 

 ization. In view of these facts we may safely assume that the 

 locus of the factor is in one or more chromosomes. When all 

 four fetuses inherit an anomaly, we must assume that the factor 

 has been equally distributed to the daughter cells of the first 

 cleavage and probably for several successive cleavages. If, 

 however, the anomaly is confined to a pair of embryos derived 

 from one half of the vesicle, it seems likely that the factor was 

 so distributed as to be totally absent from one of the first two 

 blastomeres. When only one embryo inherits the anomaly the 

 unequal distribution may have occurred during the second or 

 later cleavages. 



After a long search for some more satisfactory explanation of 

 the facts than that afforded by a resort to the mechanism involved 

 in cleavage, I have been finally driven back upon this explanation 

 by the facts immediately to be brought out in connection with 

 the phenomenon of somatic and germinal segregation. 



(c) Somatic and Germinal Segregation. The particular method 

 of polyembryonic reproduction in the armadillo is definitely 



