TECHNIQUES 353 



healing therefore indicates poor material or conditions of 

 experiment. 



Intentional disarrangement of the stripe pattern is illustrated by 

 rotating anterior halves i8o° on posterior halves. The cell is first 

 cut through halfway on one side and then gently rolled over and 

 cut through on the other side. The surface is thus completely 

 severed but the two parts remain joined by the endoplasm, the 

 first wound healing while the second is being made. Quickly, and 

 before firm rejoining of the ectoplasm occurs, the side of the needle 

 is spun around the anterior end causing it to be rotated until it 

 takes a position in which the mouthparts are now opposite the 

 primordium meridian on the posterior half. Within a minute, firm 

 healing of the parts in their new orientation will have been effected 

 and the specimen is ready to transfer. 



Regeneration, singly or en masse, can be induced by brief salt 

 treatment to cause shedding of the membranellar band. For indi- 

 vidual specimens in a drop on a sUde, I add one drop of 4% urea 

 solution, rescuing the animal as soon as the membranelles are 

 fimbriated. Shedding is completed in a large drop of culture 

 medium to which the animal is transferred for washing. Regenera- 

 tion is easily evoked in this manner, a procedure useful when 

 cutting would reduce or disarrange the lateral striping. 



When many stentors in simultaneous regeneration are required, 

 the following procedure is followed. Place 10 ml of Stentor sample 

 in a 25 ml graduated cylinder and, slanting the vessel, introduce 

 drop by drop and with minimum turbulence an equal volume of 

 4% urea (or other solution having the same effect; see p. 252). 

 Contents of the cylinder are then poured into a caster dish under a 

 dissecting microscope and follow^ed until membranelles begin to 

 be sloughed. Effective time and concentration of the salt may vary 

 with the condition of the animals. The dish is then emptied into a 

 tall olive bottle or 100 ml cylinder and quickly filled with filtered 

 lake water to dilute and stop the action of the chemical. As soon as 

 the animals settle to the bottom, the vessel is decanted and filled 

 again with w^ater for a second washing, after which the settled 

 animals are ready to be set aside or used in experiments. 



It may be mentioned here that the studies of Chambers and Kao 

 (1952) and of de Terra (1959) demonstrate that injection and 

 autoradiographic techniques are quite feasible in Stentor. 



