1918] Yocum: The Neuromotor Apparatus of Euplotes Patella 343 



If haematoxylin or its oxidation product, haematin, was to be used, 

 the best results were obtained b}^ killing the animals in hot Schaudinn 's 

 sublimate-alcohol solution. Dobell's alcoholic haematin proved to 

 be the best stain, although alcoholic iron-alum haematoxylin was 

 quite satisfactory. These two stains were best for studying nuclear 

 phenomena and were also very good for parts of the neuromotor 

 apparatus, but, due to the necessity of destaining to a considerable 

 extent in order to make the preparations usable, some of the finer 

 fibers were completely destained and rendered indistinguishable. 



If the animals were to be sectioned they were killed and dehydrated 

 in centrifuge tubes. From xylol they were transferred into gelatine 

 capsules of about three grains capacity containing paraffine. The 

 method followed was that employed by Metcalf (1908) for Opalina. 

 The capsules containing paraffine were held in a rack and set in a 

 w^arming oven hot enough to melt the paraffine. As the paraffine 

 melted the organisms settled to the bottom of the capsule. When 

 cooled the gelatine could be easily soaked off and the tip of the paraffine 

 cylinder containing the organisms cut off and put on top of another 

 capsule of paraffine. This process was repeated until all of the xylol 

 was removed. The animals were then imbedded in paraffine in a 

 Lefevre watch glass. If the animals are tinged with a little eosin or 

 erythrosin it is much easier to handle them with only a small loss. 



The sections, five to seven microns thick, were treated with either 

 haematoxylin or Mallory's connective-tissue stain. Specimens killed 

 in the picro-mercuric solution gave the best results when treated with 

 the latter dye. 



Intravitam staining was tried but no very satisfactory results were 

 obtained. Neutral red was the best dye tried and its value lay in its 

 property of staining certain external ectoplasmic structures, especially 

 the rows of granules on the dorsal side. 



Silver nitrate and gold chloride were used in an attempt to demon- 

 strate the finer fibrillar endings, but failed to give any good results. 



Some animals were studied in the living condition under a cover 

 glass. Others were killed by holding the slide with a drop of water 

 containing them over a bottle of osmic acid or chloroform. If this 

 was done for a very short time the animals were killed, but not dis- 

 torted. Such preparations were good for a study of external features 

 and were the only means by which the cirri could be studied in their 

 normal condition, for when immersed in killing fluids the cirri break 

 up into their component cilia. 



