author's abstract of this paper issued 

 by the bibliographic service, january 19 



THE EYE OF POLYCYSTIS GOETTEI (BRESSLAU) 



WM. A. KEPNER AND JOHN S. LAWRENCE 



University of Virginia 



FIVE FIGURES (ONE PLATE ) 



The rhabdocoele on which this study was made has appeared 

 from time to time during the cold months of the year in a pond 

 near the University of Virginia. It is found in greatest abun- 

 dance at a depth of about two feet when the w'ater is at winter 

 temperature. In the w'arm months of the year thej^ must seek 

 greater depths, for we have not encountered them in our sum- 

 mer collecting. Bresslau ('06), in describing the species, says: 

 "Unmittelbar hinter der Russelbasis liegt das Gehirn, auf ihm 

 jederseits am Vorderende ein Auge, dessen Schwartzes Pig- 

 ment von kugeligen Granulationen gebildet wird." (p. 417). 

 In his figure 1 he indicates a posterior black portion and an an- 

 terior clear or colorless part in each eye. The posterior portion 

 is evidently the pigmented part of the eye, while the clear region 

 is comparable to w^hat von Graff ('82) refers to in different rhab- 

 docoeles' eyes as 'Lense.' We agree, however, with Bohmig 

 ('87) when he says: "was von Graff als Linse bezeichnet, ist 

 zweifellos der beim Conserviren geschrumpfte Inhalt des Pig- 

 mentbechers." (p. 487). So that the light anterior end of each 

 eye in Bresslau's figures must be the projecting visual elements 

 seen in profile along the margin of the mouth of the pigment cup. 



Since Hesse's ('97) work, the histology of the eye of Turbellaria 

 has been well understood. He showed that there are two sets 

 of elements or cells entering the formation of the eye of the 

 Turbellaria, namely, (a) pigment-cells, and (b) visual cells or 

 retinulae. 



In all cases the pigment cells form a pigmented cup about cer- 

 tain portions of the retinulae. These pigment cups may be 

 unicellular or multicellular. So far as our knowledge goes? 



465 



JOURNAL OF MORPHOIOGV, VOL. 30, NO. 2 



