TECHNIQUES 349 



5. Cutting methods 



The simplest way of obtaining Stentor fragments is to shake the 

 animals briefly but vigorously in a tiny vial. Presumably formation 

 and breaking of bubbles adjacent to the cells splits them into pieces. 

 This was the method first used by Lillie (1896) who well knew 

 that cleaving eggs can be separated into their blastomeres in this 

 manner. If a few bits of broken cover glass are added to the vial, 

 random cutting occurs. For more precise hand sectioning needles 

 are used. Steel needles trimmed and sharpened to a very fine point 

 were used by Prowazek, Schwartz, and Weisz. I employ only glass 

 needles, made by holding the ends of two glass rods in a small gas 

 or alcohol torch flame until they fuse together lightly and form 

 a ball of molten glass between, whereupon the rods are quickly 

 separated as they are withdrawn from the flame and one or two 

 good needles are produced. The puUing must be done at just the 

 right time, w^hen the glass is neither too fluid nor too congealed, 

 and this requires practice. The glass rod should be of soft glass. 

 I do not know the specifications, but if success is not attained one 

 should try a diflFerent stock. When properly made (Fig. 97A) glass 

 needles provide the finest points obtainable and are used like a 

 knife in cutting.* 



In earlier days, ciliates were cut without quieting by merely 

 confining them to a tiny drop, beside which a large drop of 

 medium was placed, quickly to be flooded into the small one 

 immediately after the operation to prevent drying (Balbiani, 1889). 

 The best quieting agent is a solution of methyl cellulose which 

 greatly retards stentors by its high viscosity. This method was 

 introduced by Marsland (1943) for paramecia and later adopted 

 for stentor experiments by Weisz (1951a). The solution seems more 

 innocuous for stentors than for paramecia, and I noticed that it 

 quickly kills Blepharisma. Sleigh (1956), in his studies of ciliary 

 coordination, found that methyl cellulose is entirely reversible in 

 its eff"ect; and I kept coeruleus for two days in a thick solution 

 w^ithout apparent injury to the animals. Nevertheless, methyl 

 cellulose treatment sometimes showed an inhibiting influence on 

 early primordium formation (Tartar, 1958c). Early dividers in 



*Uhlig (i960) used a Spemann pipette to remove ectoplasm of the 

 fission line bit by bit to produce doublets by aborted division. 



