170 PROCEEDINGS OF THE ACADEMY OF [1895. 



if allowed to act for half an hour or more. My sections also con- 

 clusively prove the ectosarc to be quite thick and composed of 

 uniform, deeply staining rods that are packed as densely in one place 

 as another. The form of these rods as figured by several authors is 

 wholly inaccurate and misleading. For example, they are not fusi- 

 form or oval as figured by Lankester in his article Protozoa in the 

 ninth edition of the Encyclopedia Britannica, but cylindrical with 

 bluntly rounded ends. Where the collapsing vesicles ("contractile 

 vesicles ' ' of authors) are placed there appears to be a peculiar 

 separation of these rods at their inner ends to admit of the approxi- 

 mation of the vesicles to the under surface of the cuticle. 



For killing and fixing my material I found that osmic acid and 

 corrosive sublimate gave good results, both these reagents acting with 

 such rapidity ae to exclude in a large measure the production of 

 artifacts. Staining was done on the slide with hsematoxylin and 

 Biondi-Heidenhain mixture. Nuclei and food vacuoles are apt to 

 stain strongly if the staining on the slide is attempted with hsema- 

 toxylin- Very good results can also be got by staining the objects 

 in toto, as directed in the paper cited above describing my method of 

 handling such very minute objects. 



