402 ANN BISHOP 



In three cases the meganucleus was broken up into throe 

 or more rounded spheres lying in the endoplasm, the hinder- 

 most of which had passed down the body and lay as a small 

 refractive ball at the extreme posterior end. Stained prepara- 

 tions of two of these animals showed that their meganucleus 

 was composed of darkly staining granules packed more closely 

 together than they normally are but not vacuolated. Each 

 sphere of meganucleus was surrounded by micronuclei. The 

 remaining individual was isolated on a well-slide, supplied 

 with a little of the original culture medium and put into a moist 

 chamber. After about twenty-four hours it was again observed. 

 The spheres of the meganucleus were in practically the same 

 position in the anterior part, but the posterior sphere had 

 disappeared. Whether it had been absorbed or had passed 

 out of the body I cannot say ; but its position in relation to 

 the cytopyge on the previous day seemed to suggest that the 

 latter fate had befallen it. The animal was kept two more days 

 without any important changes taking place. At the end of 

 that time it died. 



The culture in which these cases were found was an old 

 leaf one. The animals in it were very few and no case of 

 division was observed while it was under observation. From 

 the lack of food vacuoles in the animals it was obvious that the 

 culture was in an impoverished state, and these abnormalities 

 were no doubt due to starvation. 



4. Methods of Cultivation. 



The first attempts to form cultures of Spirostomum 

 ambiguum were made with hay infusions. A similar solu- 

 tion to Woodruff's standard hay infusion (31) was made, the 

 formula being 10 grammes of chopped hay in 1 litre of tap-water, 

 and raised to the boiling-point for a few minutes. A culture 

 basin containing a quantity of this fluid was inoculated with 

 a few Spirostoma. In a few hours it was found that all the 

 animals had died. Experiments were then made with 75 per 

 cent., 50 per cent., and 25 per cent, dilutions of the fluid with 



