' 242 CHARLES R. STOCKARD 



that of the shoot from the terminal bud. The other top axillary 

 bud, however, was not so fortunate as its fellow and was not 

 capable of overcoming the inhibiting influence of the terminal bud 

 and so remained dormant, as is shown in figure 2, plate 5. 



Finall3\ the third possibility very rarely occurs and all three 

 of the uppermost buds are able to grow. In this case both of 

 the axillary buds had a potential or tendency of growth sufficiently 

 strong to successfully compete with the inhibiting influence of the 

 terminal bud (fig. 3, plate 5). 



We may imagine that the growth of the terminal bud in the 

 second and third cases was not normally vigorous. For some 

 reason the advantages of the two or three potential buds were 

 equalized and we find twin and triplet shoots growing out. 

 Similarly, we may imagine the potential buds around the germ- 

 ring of the fish's egg to vary in their degrees of supremacy, ordi- 

 narily only one grows and suppresses the growth tendency of all 

 other potential points. But if the developmental rate be slow, 

 the one bud fails to suppress all other points on the blastoderm, 

 and twin or triplet buds may become capable of expressing them- 

 selves. 



In conclusion, these experiments and observations make it 

 seem highly probable that influences similar to those acting be- 

 tween a growing plant bud and its resting buds, or between the 

 stronger component in a double vertebrate embryo and the 

 smaller component, are also acting between a rapidly growing 

 organ bud and other potential organ buds in the embryonic indi- 

 vidual. Such a conception has the decided advantage of being 

 of practical scientific value. Since on this basis the experimenter 

 has a logical working scheme for a study of the abnormal and 

 through this, the normal development of a given organ. Such a 

 method in an analysis of the development of the eye, for example, 

 has been most valuable. 



Summarizing the present status, I have succeeded in locating 

 more or less definitely the critical moment of origin in the follow- 

 ing individual developmental processes : 



1. The growth of the primary embryonic axis : If this be slowed 

 by arresting early cleavage stages or pregastrulation stages, the 



