NERVOUS SYSTEM OF THE TUNICATE 319 



lobes. In the case of the incurrent siphon, the chemical stimu- 

 lation of one lobe often induced closure of the whole siphon. 

 On one of the excurrent siphons there was also a complete closure 

 effected. The contraction in this case was progressive in both 

 directions from the point of stimulation around the rim of the 

 siphon. The lip-lobes were more sensitive than the tentacles to 

 the quinine. The inner lining of the pharynx also proved sensi- 

 tive to the quinine and when stimulated brought about a 

 contraction of the pharyngeal papillae andof ten a closure of one 

 or both siphons. 



The lip-lobes, tentacles, and pharyngeal lining were also sensi- 

 tive to solutions of HCl, NaCl 2n, NaOH n/10, while to 50 per 

 cent cane-sugar the same regions were unresponsive. The ten- 

 tacles move about when stimulated, but do not contract, for 

 they are stiff and apparently non-muscular organs. Often they 

 gave an upward flip when stimulated. As this might have been 

 due to the sudden ejection of water from the incurrent siphon, 

 a siphon was amputated to include the tentacles, and the ten- 

 tacles were again stimulated: they responded by rising up in a 

 concerted reaction, but not so abruptly as before. When the 

 ganglion was extirpated, this response of the tentacles could not 

 be elicited. • More data would probably have shown the con- 

 trary to be true for this latter case, since the erection of the 

 tentacles occurs for an amputated siphon which is minus the 

 ganglion and it ought also to occur for the intact siphon which 

 is minus the ganglion. 



REACTIONS OF ASCIDIA MENTULA TO VIBRATIONS 



A normally sensitive individual closes its siphon to the slightest 

 vibrations produced by disturbances in the room or by tapping 

 on the jar in which it lies. If the incurrent siphon be amputated 

 to include the circlet of tentacles, it is still capable of responding; 

 but if it is excised distal to the tentacles, it no longer responds. 

 The amputated excurrent siphon like the incurrent without its 

 tentacles also proves to be inert to vibrations. If the ganglion 

 be extirpated from an animal with both siphons intact, the 



