ORGANIZATION AND GROWTH 249 



XV. SOME CASUISTIC REMARKS ON HETEROMORPHOSIS 



1. It was my intention to analyze the conditions under- 

 lying heteromorphosis in other forms as carefully as I have 

 done in the case of Tubularia and Antennularia. Lack of 

 time, however, rendered this impossible, so I was compelled 

 to postpone these experiments. I wish, however, to add a 

 few casual observations. 



During the winter of 1889-90 I had already observed that 

 in the aquarium the stems of Gonothyrea often grew into 

 roots even when not injured externally. I thought at the 

 time that lack of light and oxygen lay at the basis of these 

 phenomena, but did not mention this fact, as I wished to 

 make it the starting-point of new experiments. For the 

 reasons given above, I did not succeed in mastering organi- 

 zation in this animal in the time at my disposal, and so 

 have again postponed further work upon these experiments. 



I have already called attention to the tendril-like bend- 

 ings of the roots of Aglaophenia pluma in paper iv. These 

 curvatures, dependent apparently upon internal causes, play 

 perhaps a much more important role than I at first antici- 

 pated. They probably are responsible for the fact that the 

 orientation of the organs, even those at a distance, does not 

 occur with the same regularity as in Antennularia. My 

 first experiments were made in very intense light, and it is 

 possible that this is the determining factor in bringing 

 about the downward growth of the adventitious roots in 

 Aglaophenia. Considering the complexity of the conditions 

 determining organization, experiments upon this animal 

 with the klinostat might prove fruitful. 



I found in Sertularia that new growths which had the 

 form of roots, but were positively heliotropic, formed a polyp 

 at their tips after they had attained a certain length, and 

 then remained positively heliotropic. According to Sachs, 

 certain substances are not only necessary in the formation of 



