208 



DYNAMICS OF LIVING MATTER 



Fig. 46. 



run parallel with the axis of symmetry of the animal from the tentacles 

 to the foot. The number of these elements may be supposed to corre- 

 spond to the number of the outer row of tentacles of the normal animal. 



Each such element behaves like a Tubu- 

 larian, with this difference, however, that 

 the elements in Cerianthus are more strongly 

 polarized than Tubularia. No heteromor- 

 phosis has thus far been produced in these 

 elements in Cerianthus, and each one is 

 able to form a tentacle at its oral pole 

 only. This fact can be nicely illustrated 

 in the following way : if a square or oblong 

 piece (abed, Fig. 46) be cut from the body 

 wall of a Cerianthus in such a way that one 

 side, ac, of the oblong is parallel to the 

 longitudinal axis of the animal, tentacles 

 will grow on one of the four sides only; 

 namely, on the side ab.* The three other 

 free edges are not able to produce tentacles. If an incision be made 

 in the body wall of a Cerianthus, tentacles will grow on the lower 

 edge of the incision (Fig. 47). 



I have recently tried whether or not by tying a ligature round the 

 middle of a piece of an Actinian this polarity could 

 not be suppressed. But the experiments did not 

 succeed, inasmuch as the cells compressed by the 

 ligature died, and through bacterial action were 

 Uquefied so that the pieces in front and behind the 

 ligature fell apart. It is therefore impossible to 

 decide whether or not a condition of the nature of a 

 current or a flow of substances in a certain direction 

 through these elements is responsible for this polarity, 

 though I consider this probable. I found, however, 

 that one condition is necessary for the growth and 

 regeneration of tentacles which also plays a r61e in 

 the corresponding phenomena in plants; namely, 

 turgidity. The tentacles of Cerianthus are hollow 

 cylinders closed at the tip, and by liquid being 

 pressed into them they can be stretched and appear 

 turgid. If, however, an incision is made in the body, 

 the tentacles above the incision can no longer be stretched out (Fig. 

 47). I have found that the turgid condition of the tentacles is neces- 

 * Loeb, UntersHchungen zur physiologischen Morphologie der Thiere. 



Fig. 47. 



