PHYSIOLOGY OF SYNAPTULA HYDRIFORMIS 355 



"Mit Sicherheit konnen wir annehmen, dass die Synapten die 

 Stellung ihres Korpers mittels der Statozysten wahrzunehmen 

 imstande sind" is, as Buddenbrock ('12) points out, mere specula- 

 tion, since there is no experimental evidence to prove it. As to 

 Becher's theory of the action of the statocyst, Buddenbrock 

 insists that it is "nicht gut fundiert" and "in die Kategorie 

 der vollig unkontrollierbaren Spekulationen gehort." From 

 his own experiments Buddenbrock concludes that our present 

 knowledge gives us warrant to assert merely that u bei Synapta 

 die Syatozysten lediglich im Dienste einer speciellen Fluchtbe- 

 wegung stehen, welche die Thiere vom der Oberflache in die 

 sichere Tiefe flihrt, und dass ihnen eine sonstige Funktion nicht 

 zukommt.'' 



b. Observational. The following experiments on Synaptula 

 hydriformis by no means prove that the statocysts function 

 as positional organs, but they furnish evidence in that direction. 



Synaptula hydriformis, in contrast to sand-digging forms, 

 is decidedly negatively geotropic. Light is so potent a stimulus 

 that several experiments in which specimens had to go towards 

 the light in order to carry out their usual response to gravity 

 failed to show any results. Experiments conducted in a dark- 

 box open at the top and placed in the center of the room were 

 successful, since in this way the intensity of the light was suf- 

 ficiently reduced. The animals have no difficulty in creeping 

 up the vertical walls of a glass finger-bowl, therefore a glass 

 plate was used for the trials. 



The least angle with the horizon which would induce the 

 synaptulas to crawl upwards was 20°. At 18° they went down 

 or to one side. At 20° 60 per cent went up, while at 23° and 

 above practically 100 per cent went up. 



I repeated Clark's ('99) experiment of gently changing the 

 position of the plate on which a Synaptula was moving. The 

 plate was held at an angle of 25° with the horizon, one edge 

 resting on the bottom of the dish, and when the animal had 

 started well on its way toward the top, the plate was gently 

 turned until an adjacent edge rested on the bottom. This was 

 done so gently that the body of the Synaptula was kept in its 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 24, NO. 2 



