Bergek, Eyes of CtibomeduscE. 



225 



the club facing inwards are called the larger and smaller (lower 

 and upper) complex eyes because of their more complex struc- 

 ture, while the other four simple eyes 

 are disposed laterally, two on each side 

 from the line of the two complex eyes. 

 All of these eyes look inwards through 

 a thin transparent membrane of the sub- 

 umbrella into the bell cavity. Besides 

 the eyes and ampulla already referred 

 to, a concretion fills the lowermost por- 

 tion of the club, and a group of large 

 cells having a network-like structure 

 and called network cells by Dr. Conant 

 fill the uppermost part of the club be- 

 tween the smaller complex eye and 

 the attachment of the club to its pedun- 

 cle. What is evidently nerve tissue, 

 fibers and ganglion cells, fills the rest of 

 the club. A ciliated epithelium covers 

 the club except where interrupted by 

 the eyes. 



A nerve ring, underneath the ecto- 

 derm of the subumbrella, passes from 

 near the origin of the tentacle at the 

 margin to the origin of the peduncle of 

 the sensory clubs a little above the 

 margin and gives off a branch to each 

 club. In the course of this nerve ring 

 are found ganglia in the interradii (pedal 

 ganglia) and in the perradii (radial gan- 

 glia). 



The structure of the four simple 

 eyes may first be considered. These 

 are little invaginated cups of epithelium, 

 the cells of which have become pig- 

 mented. Their cells are crowded very 

 closely in many places so that the nuclei 



Explanation to Fig. 2. 

 This figure represents three 

 pigmented cells drawn 

 from a maceration prepa- 

 ration of Conant's. The 

 long pigment cell (LP) 

 shows Us several processes 

 [PR) passing centrally, a 

 pigmented portion, and 

 more distally its rod {R) 

 which also branches. SP, 

 a short pigment cell, shows 

 its single central process 

 (PR), and distally its pig- 

 mented portion, beyond 

 which should be contin- 

 ued its prism with a cen- 

 tral fiber. This cell may 

 also be taken to represent 

 one of the retinal cells of 

 the simple eyes in which 

 case it should have a fiber 

 at its distal end similar to 

 cell P which is evidently a 

 cell from the simple eyes. 



