170 J. H. HEWITT. 



METHOD. 



Merotomy was performed according to the method of Calkins. 

 The animal selected was drawn up into a fine pointed pipet and 

 placed on a clean glass slide under a Greenough's binocular 

 microscope, eye-pieces 4 and objectives a. The medium was 

 then drawn off till a drop of only sufficient size for the animal 

 to swim in freely was left. With an ophthalmologist's iridectomy 

 knife the animals were cut in parts. The point was ground off 

 the knife and one edge ground to a semi-bellied shape. The blade 

 was plunged into the drop with the animal and the posterior 

 point of its edge allowed to rest on the surface of the slide. As 

 the animal passed from one side to the other of the drop, or 

 around the resting point of the knife edge, successive attempts 

 were made by moving the knife handle up and down to cut the 

 animal as it came directly in line with the edge of the knife. 



The frangibility of the cell body afforded one of the first 

 methods of securing fragments of infusoria for study. Pleuro- 

 tricha appears to be very frangible. On one occasion, experi- 

 ment 48, catching an animal on the surface of the media with a 

 sudden and forcible blast of air from a fine pointed pipet the 

 animal was broken in two. Simply drawing the animal rather 

 forcibly in the pipet was sometimes sufficient to break it in two 

 as in experiment 40. In a few of the experiments the merozoa 

 were secured by drawing the animal selected into a fine pointed 

 pipet and spurting it out forcibly on the side of the capsule. 



Animals to be stained were isolated from the capsule with a 

 fine pipet on a clean microscopical slide under a binocular micro- 

 scope. They were killed and fixed in 5 per cent, glacial acetic 

 acid in saturated mercuric chloride, stained by the Heidenhain 

 iron hematoxylin method, and mounted in xylol balsam. 



THE EFFECT OF MEROTOMY ON THE NUMBER OF MICRONUCLEI. 

 In Tables I. to V., inclusive, are recorded 27 experiments in 

 which the regenerated merozoon was recovered, successfully 

 stained, and mounted. The tables are divided according to the 

 position of the cut. They also state the exact time before or 

 after division, when it had been observed, the length of time 

 after merotomy before the animal was killed, and the number of 

 macronuclei and micronuclei found in the stained merozoon. 



