152 H. H. NEWMAN 



has furnished us with an interesting experiment in developmental 

 physiology. It is as though the experimenter were to be able to 

 cut an early gastrula of a sea-urchin into four equal parts and were 

 to be able to rear each of the four pieces to adult life, under envi- 

 ronmental conditions experimentally uniform for the four pieces, 

 and could then compare the four individuals thus produced spine 

 for spine, tube-foot for tube-foot, with the parents and among 

 themselves. The detailed results of such an experiment, were it 

 possible to perform it, would furnish fascinating data for the stu- 

 dent of genetics. Human skill, however, could never compass 

 the task of subdividing the gastrula equally or without injury nor 

 would it be possible to ensure strict equality of developmental 

 conditions for the four pieces. Yet this is just what nature has 

 accomplished for us in the armadillo. The experiment is success- 

 fully performed every time pregnancy occurs and it is our task 

 to analyze the results and to draw conclusions, a task which has 

 proven to be neither simple nor yet entirely without promise of 

 a certain measure of success. 



With this background and with what I consider to be a thor- 

 oughly adequate mass of material to work with, it becomes a 

 problem to decide on the most advantageous method of presenting 

 the results of the analysis, to determine what particular phase of 

 the subject should receive first attention. For several reasons it 

 seems advisable to proceed from the general to the particular, 

 from more typical to less typical conditions. Following this 

 scheme I shall present first the data dealing with the inheritance 

 of aggregates of meristic variates and shall reserve for subsequent 

 treatment the facts concerning the inheritance of peculiarities 

 of individual elements of large aggregates. 



The material for this study is furnished by an accurately con- 

 firmed enumeration of the total numbers of scutes in the nine 

 bands of armor of 56 male and 59 female sets of advanced quad- 

 ruplets and their mothers. All sets are excluded from this study 

 in which any fetus or mother exhibits atypical band arrangements 

 or in which the carapace of the mother was injured in such a way 

 as to render comparison with those of the offspring difficult. The 



