L920] Taylor: Neuromotor Apparatus in Euplotes 417 



made and which is held near the edge of a wide but very shallow 

 hanging drop. By slowly turning the screw for the up-and-down 

 movement, delicate changes in the degree of stress of the surface film 

 are thus effected, an outflow of endoplasm may be induced and its rate 

 of discharge varied more or less at will. As will later be described, 

 this affords a study of several interesting features including the nature 

 and extent of the ectoplasm and of the pellicle. 



Staining. — Several vital stains have been employed with varying 

 success. For the study of the external organelles, a .0001 per cenl 

 solution of haematoxylin gave the most satisfying results. This was also 

 useful in staining the fibrillar system; certain new features of this 

 system, in fact, were first seen after the animals had been subjected 

 for about eighteen hours to this stain. It was incidentally discovered 

 that a very weak solution (.001-0001 per cent) of tannic acid, after 

 eight to ten hours, distinctly sharpens the outline of the fibrillar 

 apparatus. This is apparently due rather to its effect upon the cyto- 

 plasm, affording a contrast which discloses more clearly the apparatus. 

 Neutral red (Grubler), new methylene blue R (C. C. Co.), toluidin blue 

 (Griibler) are among other vital dyes which enhanced the view of the 

 system of fibers. Usually for dissecting, however, the anal cirri fibers 

 and not infrequently the motorium with its attached fibers, may be 

 seen clearly enough under oil immersion (2 mm. Zeiss apochromat), 

 without the aid of intra vitum dyes. 



For studying specimens fixed and stained before or after dissection, 

 the several fixatives and stains employed by Tocom (1918, p. 342) were 

 used with good results. The method of picromercuric fixation followed 

 with Mallory's stain or with iron-haematoxylin was especially valuable 

 for the study of the fibers before and after they were cut. Delafield 's 

 haematoxylin stains the fibrillar apparatus even more distinctly. There 

 was some evidence that the cut fibers do not stain so deeply with the 

 iron-haematoxylin, but this has not, as yet, been definitely ascertained. 

 Much care is necessary in staining single specimens. Fixatives were 

 applied, usually hot. by means of the pipette (above referred to) under 

 the low power binocular. The specimen was then transferred to a 

 cover-slip or slide which had been treated with Meyers albumen fixa- 

 tive. After a distinct film had formed, the slide was passed through 

 the alcohols and stains, usually without detachment and loss of the 

 specimen. 



Material. — The fresh water ciliate, Euplotes patella, possesses cer- 

 tain morphological features that make it an unusually choice subject 



