470 WM. A. KEPNER AND JOHN S. LAWRENCE 



retinulae of the vertebrate eye. Prorhynchus has, as the analogue 

 of the cyhndrical or conical end organ, a solid low rhabdome, 

 while in Polycystis there is a hollow, rather high conical rhab- 

 dome (fig. 4, C, C and C"). Comparable with or analogous to the 

 ellipsoid of the vertebrate, Prorhynchus applanatus has a con- 

 cava-convex lens-shaped refractive body; in Polycystis goettei, 

 a wedge-shaped body (fig. 4, B, B' , and B"). Finally, analogous 

 to the nuclear-bearing region of the vertebrate visual cell there is 

 the nucleated region of the retinulae of both Prorhynchus and 

 Polycystis (fig. 4, A, A', A"). 



SUMMARY 



1. There are two visual cells and one accessory, pigmented 

 cell entering the formation of the eye of Polycystis goettei. 



2. The pigment cell is spheroidal with two Imnina within it. 



3. Into each lumen of the pigment cell there enters a retinula. 



4. The retinula resembles the visual cell of Prorhynchus ap- 

 planatus in that it has a third region homologous with that 

 animal's 'refractive lens-shaped body.' 



5. This homologue of the refractive lens-shaped body of 

 Prorhynchus is conspicuously analogous, if not homologous with, 

 the ellipsoid of the vertebrate retinula. 



