EFFECT OF FOOD ON GROWTH OF PARAMECIUM CAUDATUM. 87 



In conclusion, the experiments performed with food hormones 

 indicate (i) that potato extract will serve as a food but not as a 

 growth accelerator, (2) that yeast extract serves as a food and 

 stimulates growth, and (3) that the physiological condition of 

 the individual plays a large part in determining the rate of 

 division under experimental conditions. Results indicate that 

 when food supply has been reduced a change of diet causes 

 rapid increase in rate. Where food has been plentiful the rate 

 of division has not been greatly increased. 



2. EXPERIMENTS WITH GLANDULAR DIET. 



Shumway (1917) has recently made a series of experiments 

 with gland extracts. His controls were kept in a suspension of 

 hay infusion. When adrenalin and pituitary extract were 

 added these lines divided more than twice as rapidly as the 

 control and with very little difference between them. In another 

 experiment he determined to try what he termed a more crucial 

 test, i. e., keeping the experimental lines in gland suspension 

 alone without the basic food substance of hay infusion. Both 

 lines died after a few days treatment. 



For the following experiments a wild race of Paramecia was 

 collected in January, 1918. Individuals descended from one 

 original animal were put in hay infusion. On February 9, these 

 Paramecia as control lines, were isolated in depression slides in 

 a few drops of hay infusion and put in the moist chamber. 

 Within twenty-four hours the sister Paramecia were isolated 

 and the experimental lines established. The individuals were 

 fed on solutions made from the tablets prepared in the laboratory 

 of Armour & Co. The pituitary tablets were made from the 

 desiccated gland of an ox and suprarenal from the desiccated 

 gland of a sheep. The strength of the solution of the pituitary 

 gland was .35 per cent., that of the suprarenal .36 per cent., 

 being slightly stronger. 



The experiments as recorded in Table IX. and Table X. were 

 carried on for five weeks. With the pituitary solutions three 

 proportions of food were used first, control line two drops of 

 hay infusion, experimental line one drop of hay infusion and one 

 drop pituitary, second, control line three drops of hay infusion, 



