(10 7 ) 



In ge-neral, my obscrvatious O'n the lateral 'nerve of P. arch- 

 itecta agree with those of Aiidrews and Torrey. The lateral 

 nerve o^ the left side is quite conspicuous and extends from the 

 anterior end to a toi^it about one- third from the posterior end 

 of the animal. It runs along the lateral body wall until it is 

 almost in the region of the transverse septum, chen it gradually 

 passes obliquely upward in close proximity to the left nephridial 

 canal and finally is seen imbedded in the ectoderm at the side 

 of the anal papilla. f^rom this point it passes around the base 

 of the anal papilla between the anus and the mouth, and then it 

 begins to take the sairio course close to the nephridial tube on 

 the right side as i« did on the left side but it soon grows much 

 smaller in di&jneter ana finally disappears. (Figs. 76 to 67) 

 A longitudinal section passing through the mouth and anus sliows 

 the relation which the nerve cord bears to the ganglion and nerve 

 ring. (Fig. 84) Cori (4) figures such a section thj-ough P. psara- 

 nophila but he seems to have overlooked the nerve cord or axis 

 cylinder in this region. It is closely associated wit}: the cells 

 of the ganglion and lies Just a little below the latter. In an 

 oral direction from the ganglion is seen a section through the 

 nerve ring. 



If a cross section (Fig. 65) is taken through the ganglion 

 so as to cut longitudinally through the nerve cord and if the 



