87 



said tliat the structures they suj^ply also are innervated 

 from t!ie cerebral ganrlia. . : ;'ibres, it !■!»: . ., pass 

 from those structures through the anterior ganglion to the 

 cerebral, but tliat the latter .i-- the only "■^"♦ves in 

 which reflexes may be established seems not in accordance 

 with the structure of the nervous system in Teredo. It 

 seems raore plausible to regard the anterior ganp;lion as a 

 part of the visceral v^liich has been separated from the lat- 

 ter. It receives a part of the cerebro-visceral connect- 

 ive, and gives off some of the nerves that formerly were 

 given off by the visceral. 



From a theoretical standpoint, too, one would expect 

 elongated forms like Teredo and Pholas to have a more di- 

 rect connection. between the osphradia and the reflex cen- 

 tres. If the osphradia test the character of the water 

 flowing over the gills, then it is difficult to believe 

 that in a large "Ship-worm" the nerve impulse should 

 travel from them to the cerebral ganglion and back again 

 thi'ough the visceral ganglia to tliepallial nerves before 

 the siphons can be contracted and the inhalent current 

 stopped. This '.vould necessitate a course of almost two 

 metres in very large specimens. The more direct connec- 



