i4^ 



1. ikEDA i 



tlic .sjnicr ill front of tlio f^cptuin is llic prconil cavity, while back 

 of it lies the colhir cavitv. 



Denser accumulation of filires 

 in front of tlio r(_'«-u;-.s. 



1 cjivitv 



I'rcorul belt. 



recess of 

 :il cavity. 



gliou. 



IV _ 



I'reora,! 

 jueseutery. 

 Ocsopluij^us 



( 'ollar cavity 



Tentacles. 



If we now study tlie scrii's of sections (fi.i;s. -39 a-d'^), the 

 nature of this septum will l)eeome clear. Section öd a is the most 

 anterior of the four and ])asses through the hood at al)out the 

 plane of the line I-I in tke ahove wood-cut. The Avhole of the 

 p]-eoral cavity is Idled Avith the filjres of branching jneseuchymat- 

 ous eells except in the ventral median part {p.r.). This is the 

 beginnini;- of the posterior recess of the ))reoraI cavity, which is 

 limited anteriorly by a faint menil)raiieou« layer consisting of pro- 

 to})lasniic li])res only. Section od b is from about the plane of 

 the line II-II. This contains the ganglion (y^.) and ou each side 



* Unfortunately in the scries of sections tissues have undergone considerable disturbance 

 by the action of the killing reagent, but the relations of the layers remain unaltered. 



