112 BRUCE D. REYNOLDS. 



provided evaporation didn't take place. In making up the cul- 

 ture medium one part of the stock solution was taken and to it 

 were added nine parfs of distilled water giving a 10 per cent hay 

 infusion solution. When other ingredients such as sugar, alcohol, 

 etc., were used, they were mixed with distilled water in the desired 

 proportions and then nine parts of this were added to one part of 

 the stock solution. Thus, in every case the percentage of hay 

 infusion remained the same. After a tube containing some of 

 the stock solution had been opened and a part of its contents 

 used the remainder was discarded. The Arcellcr grown in this 

 medium subsisted largely on bacteria, the progenitors of which 

 were introduced with the organisms. 



(c) Pedigrees. 



"Pure" lines, or clones, were obtained by isolating specimens 

 from the wild culture and designating them, for example, as the 

 progenitors of clone A, clone B, etc. Upon dividing, the daugh- 

 ter-cell remaining in the old shell, and all of its descendents, were 

 referred to as clone A line a, while the daughter-cell occupying 

 the new shell, and all of its descendents, were denominated clone 

 A line ad. Fig. 3 expresses graphically the procedure followed. 



Generations: ist. 



2d. 3d. 4th. 5th. 6th. etc. 



Clone A 

 (Isolated 



cultures) 



FlG. 3. Diagram illustrating method employed in recording the relationship of 

 experimental animals. Those marked with an asterisk were either used for obser- 

 vations, or else discarded. 



When a different environment was imposed on one line of a 

 clone that line was designated, for instance, as clone A line SL-SU 

 (sn indicating that sucrose was added to the culture medium in 



