ORGANIC SYMMETRY IN ARMADILLO QUADRUPLETS. 1 99 



something more than this, since those individuals that have the 

 inherited anomaly in the soma also must have the factor for the 

 anomaly in the germ plasm, else how can we account for the fact 

 that whenever a mother has an anomaly it appears in one or 

 more of her offspring? 



This segregation must have occurred at a period prior to the 

 separation of primary germ layers, in order to account for the 

 strict parallelism between the germinal and somatic cells, and I 

 have reason to look back to the earliest cleavage divisions as the 

 probable time and occasion of the segregation of determinative 

 factors. This view is arrived at after considering all of the 

 available facts and I believe is justified. Strangely enough we 

 seem once more to be driven back to the cleavage stages for an 

 explanation of the phenomena of twinning, but there is a vast 

 difference between merely assuming the blastotomy origin of 

 twins and accepting the cleavage mechanism as the most prob- 

 able apparatus responsible for parallel germinal and somatic 

 segregation of inherited factors. 



Moreover segregation of inherited anomalies among individuals 

 of polyembryonic sets is one problem, while the symmetric or 

 asymmetric localization of these factors in the soma of the in- 

 dividual is another the problem of organic symmetry. 



2. The Peculiar Symmetry Relations Among Quadruplets. 



(a) Normal and Reversed Symmetry in the Occurrence of An- 

 omalies and their Significance. If no complicating factors entered 

 into the matter of the inheritance of double bands or double 

 scutes, we would expect to find a double scute of the left margin 

 of a given band in the mother inherited as a similarly located 

 double scute by all four offspring. We have attempted to explain 

 the failure of the anomaly to appear in all of the offspring of a 

 litter by positing a segregative mechanism operating during cleav- 

 age. Such a mechanism, however, appears inadequate to explain 

 the symmetry relations so peculiar to polyembryonic repro- 

 duction. 



The mirror-image type of symmetry is normal for the antimeric 

 halves of a single individual and exceptions to or breaches of the 

 mirror-image type of symmetry affords a new problem. Double 



