Light-and clarl;-nclal)tatioii of the cimtaceaii coiiipounil eye includes iiioveineiits of tlie retinal pigments. Although illuiiii~iation is 1mom-n to be an inipoi.taiit factor iii deterniiiiiiig the position of tlic i.ctiiia1 pigmetits, the nieclianisni wliicli controls pigiileiit inigratioii is iiot fully understood. Tlic \videspread occiii~eiicc~ of persistriit tliuriial rh>-thiri of oiie or inorc of the i.etiiia1 pigments iiiclicates tlint factoix otlirit tliaii light must be taken into ;wcouiit. 111 1930 TTc.lsli tl e s c i * i 1 ) e cll a per si s t P 11 t (1 i uiw a1 rl i y t lini of 1.e t i iia 1 pipriel it iiiigixtioii for tlie prawn, .llnc.rol/i-trc7rii/ri/. Ile snggcstccl tliat I)oth IIOI'VOLIS mid I I O ~~~I O I I ~I ~ J1iecli:lnis;ui.: iiiiglit be iiivolved. S i i n i c ~~) u s i'cports of persistent diuriinl i*liptlinis of various i.otiiial pigmcnts l i n ~c i 1 ~~1 ~~~a r < ~( l . Snniinayics of reported retiiial pigment i*liytlims ( T ~J W W ~I , '44 ; Klt~iiiliolz, '49) diow tlii~t aiiy one or almost aiiy conibinatioii of pigiiiciits may he involved iii the persistent rliytlim. Iii some cases a r h ~t l i n i persihts in coiistaiit light, in other cases oulp in constant , and in some cases tlir i*li~-tlini persists both in cons t ant light a iid c oiis t an t dai81iiie s s. *This inIestigntion n e s supported in part by n research grant fioiii the Giadiiatr Hc 11001 of Sortlrv estriu r'airersity. 103 11. &IARQI'FXZITE T E B G AKD E'RAKK A. RROTI'S, JR.
I<nowles ( '50) reported his investigations on L e a d e r scrrtrtzcs. R e found that there is a diurnal rhythm of the proximal and reflecting pigments which persists in constant clarkiiess. After removal of the sinus glands the rhythm was still present. IIe furtlier reported that migration of tlie prosi-ma1 pigment in response to light was uiiaflected bj-sinus gland rcniovirl. The effect of sinus gland removal on the distal pigiiient, which does not show a persistent rhythm, was less clear. In some of the operated animals the distal pigment remained in the dark-adapted condition regardless of illumination ; in others some movement toward light-adaptation was observed. 111 no case was complete light-adaptation of the distal pignieiit obtained in the absence of the sinus glanci.