204 STUDIES IN GENERAL PHYSIOLOGY 



in Naples I did not find a single exception to this rule. 

 When a piece was cut from the stem of Antennularia anten- 

 nina and a new stem grew out of it, either through regenera- 

 tion or through heteromorphosis, the newly formed stem 

 had, under ordinary circumstances, all the characteristics of 



the old it grew upward with- 

 out branching. 



Under certain external con- 

 ditions, however, an entirely 

 different kind of stem was 

 regenerated. At first a short 

 stem grew straight and verti- 

 cally upward, but from this soon 

 sprang a new branch having the 

 diameter of the old. Since 

 every branch one after another 

 gave rise to other new lateral 

 branches, which after a time no 

 longer grew perfectly vertically 

 upward, forms of Antennularia 

 with many ramifications 

 originated. Faithful represen- 

 FIG - 51 tations of three such forms are 



given in Fig. 51. They all arose from stems lying absolutely 

 horizontal, or nearly so, two at the apical end and one at 

 the basal end. No branches were formed. 



I have, moreover, made experiments to decide whether 

 pieces of the old stems which under abnormal conditions 

 gave rise to variations would produce unbranched or branched 

 antennina stems when brought back to normal conditions. 

 Under these conditions they formed only unbranched anten- 

 nina stems. 



Under the abnormal conditions, however, not all the stems 

 branched ; this happened only in part of the specimens. 



