90 



The Mechanistic Conception of Life 



Tower was kind enough to draw for me, shows a branch which 

 formed roots at its apex and polyps at its roots in this manner. 



Fig. 27. — Heteromorphosis in Margelis, a hydroid. At a and b, where the 

 points of stems touch the ground of the aquarium, new roots or stolons grow out. 



The stem touched the bottom of the dish with the apical ends, 

 a and b. All these ends gave rise to roots. From the upper 

 side of the original root, which was not in contact with the 



Pig. 28. — Heteromorphosis in Pennaria. A piece a b ot this hydroid was cut 

 out and put into a jar with sea-water. The ends a and 6 touched the bottom of the 

 jar. At both points new roots grew out. 



glass, later on small polyps grew out. Every place which 



was in contact with solid bodies gave rise to roots, and every 



place which was in contact with sea-water gave rise to polyps. 



This is not the only species of hydroid found at Woods Hole 



