author's abstract of this paper issued 

 bt the bibliographic service august 6 



EFFECTS OF LIGHT AND DARKNESS ON THE EYE OF 

 PRORHYNCHUS APPLANATUS KENNEL 



WM. A. KEPNER and A. M. FOSHEE 



University of Virginia 



THREE TEXT FIGURES AND ONE PLATE 



The eye of Prorhynchus applanatus Kennel consists of but 

 two cells. One of these cells is the pigment cell and the other 

 is the \dsual cell or retinula (figs. 1 and 2). The earliest investi- 

 gators in this field recognized that a pigment-cup was associated 

 with the visual elements of turbellarian eyes. In 1864 Leydig 

 described in part the contents of this cup; but it was not until 

 Hesse's ('97) work that we get a satisfactory account of the 

 structure of the visual cells and pigment-cup and the relation 

 between them. In one respect the work of Kepner and Talia- 

 ferro ('16) has carried the knowledge of the cytological details 

 of the eye of this rhabdocoele beyond Hesse's observations, as 

 will be later indicated. 



The material and methods of fixation of the specimens for 

 this work were on the whole similar to those used by Kepner and 

 Taliaferro. The specimens have been collected by bringing 

 into the laboratory pads of Vaucheria and other plant masses 

 from the face of a dam over which water continually flows. 

 These masses of algae and higher plants were placed in large 

 glass vessels in tap water. The animals within forty-eight 

 hours made their way to the surface in such aquaria where they 

 were readily collected and transferred to embryological watch 

 glasses that contained spring water. One part of each col- 

 lection was placed during the day (from 9.00 a.m. until 5.00 p.m.) 

 in the northern light of the laboratory from time to time during 

 the months of April and May. At 5.00 p.m. each day a 40 

 Watt, 110 volt, Fostoria Mazda light lamp was turned on as 

 it hung with its glass wall 21 cm. above the surface of the water 



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