Physiological Morphology 



87 



grew downward, and the apical end, a, had formed a new 

 stem, S. 



A similar piece was cut out from another specimen and was 

 hung upside down in the aquarium (Fig. 24). The root end h, 

 which was now above, formed a new stem, S, and the apical 

 end a, which was below, formed roots, W. In the newly 

 formed stem the arrangement of the organs was the same as 

 in the normal animal, namely, the branches which were growing 



Fig. 25. — From nature. Regeneration of a piece o h cut out from the stem 

 of Antennularia and put horizontally into the water. The branches on the lower 

 side whicli had ceased to grow, grow downward as stolons and attach themselves 

 to solid bodies. On the upper side a new stem c d grows vertically upward. 



obliquely upward bore polyps on their upper side. From this 

 we see that it was possible to substitute a root for a stem and 

 an apex for a root. This phenomenon of the substitution of 

 one organ for another I termed heteromorphosis. If the excised 

 piece of an Antennularia was placed horizontally instead of 

 vertically in the aquarium, something still more remarkable 

 occured, namely, the branches on the lower side suddenly began 

 to grow vertically downward, and these downward growing 

 elements were no longer branches but roots (Fig. 25). This 

 could be proved by their physiological reactions, for the roots 

 attach themselves to the surface of solid bodies, e.g., the glass 



