Vol. XXVII. October, 1914. No. 4 



BIOLOGICAL BULLETIN 



REGENERATION OF PLEUROTRICHA AFTER MERO- 

 TOMY WITH REFERENCE ESPECIALLY TO THE 

 NUMBER OF MICRONUCLEI AND THE OC- 

 CURRENCE OF UNINUCLEATE CELLS. 1 



J. H. HEWITT. 



Lewin, 1 working with Stylonychia, has reported a series of 

 experiments in which, after merotomy, he observed an increase 

 in the number of micronuclei in the regenerated merozoa. It 

 was thought to be of interest to repeat Lewin's experiments on 

 another member of the hypotrichus group to determine if there 

 might be any general application of the phenomenon he had 

 observed. Pleurotricha was chosen for the experiments. 



MATERIAL. 



The animals used were secured from a strain, the originator of 

 which was isolated by Dr. George A. Baitsell in the biological 

 laboratory of Yale University. The strain had been adapted to 

 laboratory hay infusion media and was preserved as a stock 

 culture in sterile test-tubes plugged with cotton. Such a culture 

 tube of organisms was given me and from it subcultures were 

 made to other tubes of fresh media and to fresh media in small 

 glass capsules. 



The hay infusion used as medium was prepared by placing 

 about 10 grams of field hay in 200 c.c. of tap water in an Erlen- 

 meyer flask and boiling it over a bunsen burner for a few minutes. 

 This medium was made up but once and was used in the pro- 

 portion of one drop of the infusion to five drops of tap water, 

 this amount of fluid in a capsule serving as the medium for a 

 single animal for twenty-four hours, or till it divided. 



1 From the Marine Biological Laboratory, Woods Hole, Mass. 



169 



