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. 
Digitized by Microsoft® 
