HEREDITY AND ORGANIC SYMMETRY IX ARMADILLO. 13 



would be too tedious a task to draw each anomaly in detail after 

 the fashion of Figs. I and 3. Instead I shall use the diagrammatic 

 form seen in Figs. 2 and 4, which give all the necessary informa- 

 tion. The best method I have been able to devise for showing 

 the symmetrical or asymmetrical relations of the anomalies and 

 their distribution among the quadruplet fetuses of a set is that 

 shown in Figs. 9-16, in which the anomalous bands are placed 

 as though within the embryonic vesicle. The reader must 

 remember that the structures studied are integumentary units, 

 that the embryonic vesicle is so inverted that the ectoderm forms 

 the inner lining and the endoderm is on the exterior. 



The diagram (Fig. 8) shows the relative positions of the band 

 anomalies of the fetuses in set 87 (Fig. 9). Here we have an 

 equatorial cross section of an advanced vesicle with the body 

 of each fetus severed at the first armor band where the anomaly 

 occurs. The ventral surfaces face outward and are attached 

 by their respective umbilical cords to the placental portion of 

 the vesicle. The dorsal aspects are turned inward. Right and 

 left sides of each fetus are indicated. The reader must imagine 

 himself in the center of the vesicle facing outward toward each 

 fetus. In order to simplify this type of diagram, I have found 

 it best to ignore all structures but the band in question and to 

 represent the latter as though straightened out against the 

 periphery. The reader will understand the adopted form of 

 diagram after a comparison of Fig. 8, which represents nearly 

 the actual relations present in set 87, and Fig. 9, which is a 

 diagram of the same set showing only the bands that are of 

 interest in this study. In both figures the solid quadrant line 

 divides the twins I. and II. from twins III. and IV. and the 

 dotted line separates twin individuals, I. from II. and III. from 

 IV. In the actual vesicle these quadrant lines are occupied by 

 amniotic partitions that hermetically isolate each fetus from 

 the others. When the anomaly is found in the mother also the 

 material condition is indicated in a straight band diagram beside 

 or beneath the circle showing the offspring. When any individual 

 shows an anomaly in more than one band, the more anterior 

 anomaly is. shown in the circle and the more posterior anomaly 

 in a concentric sector outside of the circle, as in Fig. 9. 



