REGENERATION IN PARAMECIUM CAUDATUM. 155 



meganucleus. The brevity of the paper makes it difficult to 

 determine how this result was brought about. I have not been 

 able to find a more complete account of these preliminary 

 experiments. 



In June, 1911, while working in Professor Boveri's laboratory 

 in Wiirzburg, I made a series of experiments on large races of 

 Paramecia from Munich and Wiirzburg, and up to May, 1912, 

 these pure lines were used for comparison with material collected 

 in Bryn Mawr. During the course of my investigations a paper 

 appeared by Calkins ('n) in which he describes in detail the 

 behavior of fragments of Paramecia after the removal of some 

 of the cytoplasm. My results confirm those of Calkins so exactly 

 that I shall omit a full description of the individual experiments 

 merely giving a summary of the results in tabulated form. 



It gives me pleasure to have this opportunity to express my 

 gratitude to Professor Boveri for the many courtesies extended 

 to me during my stay in Wiirzburg, and to Professor Jennings 

 for his kindness in supplying me with some of his pure lines. 



METHODS. 



The methods followed were practically those used by Calkins 

 except that instead of treating the cells with neutral red before 

 cutting them, the animals were quieted by placing them in a 

 small drop of tap water thickened with quince seed. Immedi- 

 ately after the operation a few drops of culture fluid were added. 

 All cultures were kept in hollow slides in a moist chamber. The 

 culture medium was changed every twenty-four to forty-eight 

 hours as conditions required. The infusion made from Timothy 

 heads, according to Jennings' method, was the culture fluid most 

 generally employed. A most satisfactory culture medium if 

 rightly used is a .2 per cent, solution of Horlick's Malted Milk. 



EXPERIMENTS. 



A. The Behavior of Cells after Removal of Part of the Cytoplasm. 



Thousands of Paramecia were cut during the course of these 



experiments. The fragments were examined four hours after 



the operation and then again on the following day. All fragments 



