88 



The Mechanistic Conception of Life 



of the aquarium, while the stems never show such a reaction. 

 These new parts growing out from the branches of the under 

 side of the stem attached themselves to the solid bodies with 

 which they came in contact. Moreover, they were positively 

 geotropic (that is, they grew toward the center of the earth), 



while the branches never 

 showed any positive geo- 

 tropism. The branches 

 on the upper side were 

 not transformed into 

 roots. They either per- 

 ished or gave rise to long, 

 slender, perfectly straight 

 stems, which grew ver- 

 tically upward. These 

 stems, as a rule, were too 

 slender to bear branches, 

 but at parts of the 

 upper surface of the 

 main stem there origi- 

 nated new stems (c d, 

 Fig. 25), which grew 

 vertically upward and 

 produced the typical 

 little branches bearing 

 polyps. 



If we brought the stem into an obhque position (Fig. 26), 

 with the apex a upward, from every element of the main stem 

 new stems and roots originated, but with this difference, that 

 stems always originated from the upper side of an element and 

 roots from its lower side. If the stem were placed in an oblique 

 position, with the root end above, the branches on the mider 

 side grew out as roots, and at the upper end a stem arose as 

 usual. 



Fig. 26. — Diagrammatic regeneration in a 

 piece o b of a stem of Antennularia put ob- 

 liquely into the water. On the upper side of 

 the stem a b new stems S, S„ S,„ grow verti- 

 cally upward, while at the lower end of the 

 piece a b opposite the new stems roots W, 

 W„ W,„ grow out. 



This influence of gravitation is foimd only 

 in Antennularia antennina, not in other forms 

 of Antennularia. 



