530 WALDO SHUMWAY 



Certain substances which produce decreases in the rate of di- 

 vision have been carefully studied by Woodruff (summary and 

 literature list, 1912). While on the other hand several sub- 

 stances have been reported to produce the opposite effect, less 

 evidence has been adduced either as to the effect or its nature. 



In 1912 I commenced feeding experiments upon Paramaecium, 

 using the substance of the thyroid gland. In 1914 I was able to 

 show that this substance produced great increases in the division 

 rate of a pedigreed race of Paramaecium aurelia. In that paper 

 I reviewed experiments of Nowikoff ('08), who had arrived at 

 somewhat similar conclusions through a different method of in- 

 vestigation. Since that time Budington and Harvey ('15) have 

 reported experiments using the thyroid substance from fish, 

 amphibia, reptiles, birds and mammals which confirm the results 

 I obtained from mammalian tissue. 



Meantime I have carried my investigations further with a view 

 to confirming my results on Paramaecium aurelia by similar ex- 

 periments on P. caudatum; to ascertain whether the effect pro- 

 duced by the thyroid is unique among the internally secreting 

 glands and by what fraction of the thyroid it is produced, what 

 effect continued thyroid feeding might have upon the life cycle, 

 and what other effects on the activities or structures of Para- 

 maecium might be discovered bearing on the nature of the thy- 

 roid effect. While definite answers to all these queries have not 

 yet been obtained, the data collected may be brought together at 

 this time, and certain conclusions obtained. 



The experiments here reported have been carried on in the 

 Zoological Laboratory of Columbia University, "the Marine Bio- 

 logical Laboratory at Woods Hole, and the Biological Labora- 

 tory of Amherst College. For the preparation of desiccated 

 glands I am indebted to the Research Laboratory of Organo- 

 therapeutics of Armour and Company. From my colleagues at 

 Amherst I have received many helpful suggestions in the prepa- 

 ration of this report. I take this opportunity, finally, to ex- 

 press my sincere thanks to Prof. Gary N. Calkins, at whose sug- 

 gestion these experiments were commenced and whose critical 

 advice has assisted their prosecution. 



