THE EYE OF PECTEN. 69 



of polygonal cells with thick walls. Patten described them 

 as irregular with excentric nuclei, which appear iu many- 

 cases to have disappeared from the cells near the inner sur- 

 face. Rawitz described them as polygonal and membraneless 

 with small nuclei, and Schreiuer terms them "pretty large" 

 vesicular cells, the peripheral ones flattened, with a large 

 nucleus and no cell-membrane. The latter writer noticed, 

 that in sections of the lens some cells appeared to be without 

 a nucleus (see PI. 6, fig. 1), but went no further into the 

 question. 



Hesse says (34) the lens "besteht wie sclion lange bekannt, 

 aus zahlreiclien, dicht neben einander gepackten Zellen, 

 deren Korper sich an einander abplatten und bisweilen 

 eigenthumliche Formen auf den Durchschnitten zeigen." 



Later he adds (p. 395) "... da man ferner aus einem 

 Durchschnitt auf die Gesammtgestalt der Zellen nicht 

 schliessen kann, so ist es nicht moglich liier einen Zusam- 

 nienhang zwischen Lage des Centralkorperchens und Gestalt 

 der Zelle festzustellen/' Hesse, however, did not adopt any 

 maceration methods to solve tlie difficulty presented by 

 sections. In sections through the lens, whicli is well pre- 

 served in formol-fixed specimens or Hermann-sublimate, tlie 

 cells only rarely possess a polyliedral shape, in fact it is 

 only here and there that they appear sharply angular. The 

 cell contours are very distinct and appear rounded, so that 

 there are irregular oval, pear-shaped and long band-shaped, 

 cells (PI. 7, figs. 5 and 6). The size, too, varies considerably, 

 and. a very small, apparently non-nucleated cell may adjoin 

 a large one. If, however, this small cell be followed, through 

 several sections, it will be found to be merely the continua- 

 tion of a cell which is elongated to an extraordinary degree. 

 The true shape of the cells was found after macerating the 

 eye in 2|-3 per cent, chloral hydrate solution in sea-water for 

 four to six hours. This medium preserves admirably the 

 delicate processes of the cells, and the preparation gives the 

 lens-cells, separated, uncontracted, and with all details of 

 structure undamaged. 



