99 



The following data gives the number of retinal cells found in each of a 

 series of cross sections. Sections are 65 ," thick and counted from in front : 



No. of Sections. No. of Cells in Retina. 



1 to 8 



8 11 



9 19 



10 20 



11 27 



12 33 



13 33 



14 28 



15 27 



16 20 



17 7 



18 7 



19 5 



20 



21 11 



22 13 



23 10 



24 10 



25 5 



26 6 



27 



28 8 



29 4 



30 2 



31 



32 



Total 327 



In P. exilipes there is a space between the basement membrane of the 

 hypoderm and the membrana propria of the optic ganglia, which is occupied 

 by the fine fibers which connect the ommatidia and optic ganglia. In P. 

 antrorum this space is filled with coagulated haemolymph (Fig. V). This 

 haemolymph is in circular or angular blocks. These blocks begin about 40 // 

 from tip of eye and extend back through a space of about 60 or 70 fi to the 



