1914] Little: Ocelli of Pol ijorchis 309 



paraffin was then added, and finally into melted paraffin (55° C.) 

 for about fifteen minutes. The sections were cut three, six, or 

 seven microns thick and mounted in the usual way. 



Many complications arose in the process of staining, for 

 many of the ordinary dyes produced little or no difiPerentia- 

 tion. Safranin, carmine, methylen blue, light green, and several 

 other dyes were tried, but with unsatisfactory results. Iron- 

 alum haematoxylin with a number of counter-stains was tried, 

 but these proved of little value. Delafield's haematoxylin with 

 eosin was fairly satisfactory and for the study of pigment was 

 perhaps the best stain of all tried. For a general differentiation, 

 Mallory's connective tissue stain with acid fuchsin gave excellent 

 contrasts, though the cell structures were not so well defined. 



The best preparations were obtained with the material fixed 

 in Zenker's or Bouin's fluid and stained with Mallory's phos- 

 photungstic acid haematoxylin, used as follows at room tempera- 

 ture : 



Potassium permanganate, 0.2% 8 to 10 minutes. 



Oxalic aeid, 2% 10 minutes. 



Phosphotungstie aeiJ haematoxylin 12 to 14 hours. 



The tissue for the above formiila should be fixed with Zenker's 

 fluid. If Bouin's is used, the slides should remain for at least 

 twenty minutes in the potassium permanganate. 



For maceration preparations the Hertwigs' (1878) plan was 

 followed. The fresh tissue remains in equal parts of 0.05 per 

 cent osmic acid and 0.2 per cent acetic acid for about two 

 minutes, and is then washed several times in 0.1 per cent acetic, 

 in which it then remains for from twelve to twenty-four hours. 

 The eyespots can then be easily teased or shaken loose from 

 the tentacles, mounted in glycerine and Beale's carmine, and 

 disassociated by tapping upon the coverglass, 



STRUCTURE 



The animal is bell-shaped. The sides are nearly vertical. 



becoming rounded or almost hemispherical at the aboral end 



(pi. 13, fig. 1). Fewkes (1889) describes a conical projection or 



thickening at the top, but of all those specimens examined by me 



