358 A. RICHARDS. 



periods at the same time intervals as the control lines, and thyroid 

 produces the greatest acceleration of the division rate when the 

 control line is dividing most rapidly." In one experiment, how- 

 ever, the use of thymus, adrenal, and pituitary substances also gave 

 an acceleration of the rate of division, but other experiments did 

 not confirm these data. 



In experiments which are somewhat similar to those of Shum- 

 way, Miss Chambers obtained results which indicate that the divi- 

 sion rate of Paramecia was increased by the feeding of ground 

 yeast, of pituitary preparation, and especially of suprarenal solu- 

 tion. In the latter case ''these results are more constant than 

 those obtained by feeding pituitary solution. There is a slight but 

 decided increase over the control lines." 



Paramcecmm has been the subject of a number of experiments 

 of this sort, for it has responded by alterations of its division rate 

 to several kinds of stimuli. Calkins and Lieb found that one part 

 of alcohol in about 2,500 parts of culture medium acted continu- 

 ously to accelerate the division rate. Woodruff has shown that 

 the effect of small amounts of alcohol on Paramcecium and Stylo- 

 nychia as well is to produce a much more rapid rate of division in 

 the experiment than in the control during the first month of the 

 work, but after that the rate decreased as compared with the con- 

 trol, and this is followed by fluctuations both above and below the 

 control. Woodruff had earlier shown that dibasic potassium phos- 

 phate (K 2 HPO 4 ) caused an acceleration of the rate of division 

 during the early part of the cycle of an Oxytricha fall ax culture, 

 and a retardation during the latter part. Potassium sulphate 

 (K 2 SO 4 ) and potassium bromide (KBr) in n/ioo solutions like- 

 wise caused slight acceleration. The stimulating effect of the 

 treatment gradually wears off and the agents become depressants, 

 but an increased dose will again cause a stimulation. The tem- 

 porary effect of alcohol upon the rate of division of Paramcecium 

 reminds the writer of his own observations on the effect of x-rays 

 upon the rate of cleavage of Planorbis eggs. 



The effect of oxygen upon developing eggs has been studied by 

 a number of investigators with various problems in mind. In one 

 case results were obtained which allow conclusions to be drawn 

 as to the effect upon the rate of division. Godlewski found that 



