158 Messrs. H. G. Thornton and G. Smith. 



bacteria in the culture usually interferes with the Euglena growth. The 

 following culture may be regarded as typical of the growth of Euglena in 

 a medium of this nature : — 



Cultures with Tyrosin Media, inoculated February 2. 



Composition of tube. 



Growth on Feb. 5. 



Growth on Eeb. 18. 



4 c.c. Miquel tap + 6 c.c. tap water + solid 

 tyrosin 



4 c.c. Miquel tap + 6 c.c. tap water + 1 c.c. 

 tyrosin solution 



Very strong Euglena 

 growth. 



Slight growth of 

 Euglena. 



Euglena dead or 



encysted ; numerous 



bacteria. 

 Very strong Euglena 



growth ; very few 



bacteria. 



To avoid the excessive growth of bacteria in the tyrosin and at the same 

 time to ensure the continuous supply of tyrosin, the following culture method 

 was devised. The Euglena was grown in a tube containing the optimal 

 Miquel mixture alone, and the trace of tyrosin was supplied from another 

 tube containing a saturated solution of this substance connected by means of 

 a capillary tube with the Euglena culture. In this way the culture medium 

 is continually supplied with traces of tyrosin solution, but the diffusion is 

 too slow to cause an excess of tyrosin in the tube containing the Euglena. 

 It was found that by this method a strong growth of Euglena could gradually 

 be obtained, nearly free from the bacteria and minute flagellates which 

 always appeared in cultures to which solid tyrosin was added. 



Of all the culture media employed the thickest and most successful 

 growths of Euglena have been obtained with optimal Miquel mixture to 

 which tyrosin is added. 



Glycocoll. — Cultures were made in optimal Miquel mixture to which was 

 added 1 c.c. of 1-per-eent. solution of glycocoll. These cultures invariably 

 gave a strong growth of bacteria and, at first, a greatly retarded growth of 

 Euglena, though subsequently the Euglena increased. In no case did these 

 cultures compare in strength of growth with the cultures in tyrosin media. 

 It is probable that this retardation was due to the bacterial growth, and this 

 subject will be dealt with in the latter part of the paper. 



Alanine. — 1 c.c. of a 1-per-cent. alanine solution was added to the 

 Miquel mixture as usual. The cultures invariably gave a very strong- 

 bacterial growth, and very frequently a bacillus producing a vivid apple- 

 green coloration appeared. This green colouring matter was shown not to 

 be chlorophyll, as it was developed more rapidly and to a greater degree in 

 the dark than in the light. At first, as in glycocoll, the Euglena failed to 

 multiply, though after a long period, viz. about three weeks, tubes inoculated 



