EXPERIMENTS ON ASCIDIANS 41 



these organs, and this stimulation is said to cause the 

 contracted sphincters to relax. Goltz and Ewald 

 have found, however, that after extirpation of the en- 

 tire spinal cord up to the cervical part, defalcation and 

 urination still occur normally (4). Only for a time after 

 the operation the sphincters are relaxed. Later on 

 everything again becomes normal. These phenomena 

 probably belong to the same class as the one already 

 described in the Ascidian. The processes in the 

 normal evacuations of the bladder and rectum are not 

 determined by the morphological structure of the so- 

 called reflex centre, but by the muscles of the bladder 

 and of the rectum themselves. The spinal cord 

 serves only as a more sensitive and quicker conductor 

 for the stimulus. Goltz and Ewald are inclined, it is 

 true, to assume that, after all, ganglion-cells or un- 

 known nervous structures determine these results. 

 But the fact that the muscles of the skeleton can be 

 caused to contract rhythmically when put in the right 

 solution, makes this assumption unnecessary ; more- 

 over, the facts of comparative physiology must also be 

 taken into consideration. The Actinia mesembryan- 

 themitm of the East Sea and the Mediterranean per- 

 haps show fewer differences morphologically than the 

 sphincter ani and the gastrocnemius, and yet the 

 Actinia mesembryanthemum of the Mediterranean 

 shows a form of irritability which the Actinian of the 

 same name from the East Sea does not show, namely, 

 negative geotropism. I mention this illustration, to 

 which many others might be added, in order to show 



