1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 341 



TECHNIQUE 



Culture 



Since Euplotes can be found in almost any pool of standing water, 

 it is not a very difficult matter to culture the animals in the laboratory. 

 Euplotes patella, the organism which is the subject of this investiga- 

 tion, was kept in an old aquarium in the laboratory for over a year 

 and seemed to thrive without the supplying of any food. However, 

 these animals suddenly decreased in number, apparently due to the 

 presence of great numbers of Paramoecium hursaria, until they finally 

 disappeared altogether. 



It was then found necessary to find some means of culturing 

 Euplotes. Several culture media were tried with varying degrees of 

 success. A weak solution of beef extract failed to give any satisfactory 

 results. Hay infusions such as are used for obtaining Paramoecia for 

 class work, seemed to be excellent for a while, as in these cultures 

 Euplotes associated with Stylonychia were found in abundance. The 

 ciliates in such cultures died after a week or more, probably because 

 the infusion was too strong and became too sour. 



The medium most used was a 0.25 to 0.50 per cent solution of 

 Horlick's Malted Milk. In these cultures the animals have been kept 

 for several weeks by adding water to overcome the loss by evaporation 

 and occasionally a small amount of the milk. Such a medium seems 

 best suited to supply the necessary bacteria, small flagellates and 

 ciliates, which constitute the food of Euplotes. Fairly good results 

 were also obtained by boiling dried mushrooms and diluting the in- 

 fusion to a low percentage. 



Small beakers of 250 cubic centimeters capacity were used as con- 

 tainers for the cultures, and in these the Euplotes associated with 

 StylonycJiia and Paramoecium often formed a light gray line on the 

 glass just beneath the surface of the water. In case a scum of mold 

 formed over the medium, Euplotes could always be found on the under 

 side of the scum. By taking a drop of water from near the top of the 

 culture the specimens could usually be collected in sufficient numbers 

 for study. 



Methods of Preparation 



For stained preparations the cover-glass method was largely em- 

 ployed. If Euplotes was sufficiently numerous, drops of w^ater could 

 be taken directly from the cultures and put on the cover glasses which 



