(109) 

 structure back o^ the anal papilla, on the siaes, it dimiriishea 

 in size until its cella become indistinguishable from those of 

 the nerve rin.-. In fact, all of the ectoderm fortiiin.: the sides of 

 the re eve between the anal papilla and the base of the lopho- 

 phore i^ rich in nerve fibers and cells. 



The nerve rinjj fcllov/s tre base of tlie lophophore on the 

 outer side throue,hout its extent and in the inner part o-f" the 

 horse-shoe, it is quite rich m nerve cells whose processes can 

 be seen penetrating into the mass of fibers, (Figs. 67 to 74) 

 This ring represents the collar nerve ring of the Actinot rocha. 



There is a definite tract of nervous tissue running up the 

 inner side of the tentacle but 1 am not prepared to say that it 

 is a nerve naming from the ring although it is nervous tissue 

 v.hich is undoubcedly continuous v.'ith that of the nervu ring, 



Cori (4) has carenUly studied the anatomy of the lop'^o- 



phoral orgajn of P. psammophila and 1 have nothing to aad to his 



or no t 

 description at present, I am also unprepared to say whether}^ the 



second la:,er of the lophophoral organ consists of nerve cells, 



As he has described, they have lon^, prolongations ';^.ich 



extend from the cells of the inner layer to the outer and these 



processes f o m a rather marked layer just below tl;e epidermis on 



the outer surface o^ the organ. At the base o- t^.e lopho,horal 



orgaii, these prolongations seem to be intimately associatea with 



