OBSERVATIONS ON POLYZOA. Ill 



has been discovered by Fritz Miiller in Seriolaria. * He re- 

 marked in fact the same phenomena in Lophopus crystal- 

 linns, which led Miiller to begin his investigation ; namely, 

 that when the coenoecinm was touched all the polypides 

 were alarmed, whereas, when a single polypide was dis- 

 turbed it alone retracted . 



I have examined witli care all parts of the evaginable 

 endocyst in other genera in order to hnd this colonial system, 

 but without success. The only nerve-branch which might 

 connect the nerve-mass with a general stalk would be the 

 polypidal nerve-branch. This, however, appears to spread 

 itself out on reaching the evaginable endocyst into a multi- 

 tude of filaments too minute to be successfully followed. 



The tentacles are the only tactile organs, and, as previ- 

 ously described, are the only means possessed by the poly- 

 pides of receiving impressions from without. 



The polypides are not sensitive to light. At ordinary 

 temperatures even the darkness-loving Fredericella may 

 be exposed for a time to the direct rays of the sun with- 

 out any visible result, although but just removed from the 

 perpetual shade in which it had previously lived. The 

 loudest noises prove equally ineffectual ; in a word, the}^ 

 remain fully expanded and confidently at ease until the 

 water is ao-itated. 



The epistome has been thought to be an organ of taste, 

 and certainly, besides its position, it has a pliability which 

 would seem to confirm such an opinion. The border is 

 capable of a tactile motion similar to that of the human 

 tongue, and it takes cognizaace of what passes into the 

 mouth by frequent and repeated jerks towards the aperture. 

 Although used in closing the mouth in order to retain the 

 food, I have never yet seen it prevent the entrance of any- 

 thing. This duty, as previously explained, falls to the lot 

 of the surrounding tentacles. 



Digestive System. 

 The layers of the alimentary canal are the same 

 in number and have very nearly the same character as tliose 



*Fritz Muller. Das colonialnerven-systein, Arcliiv fiir. Naturg. 

 Bd.l,p. 311, 1860. 



