2O2 GARY N. CALKINS. 



composition of Paramoecium wears out or disappears so that the 

 ferment-forming activity is lessened. A change of diet restores the 

 power. The restoration may be effected, not only by the extract 

 of beef, but by clear chemicals as well. Thus potassium phos- 

 phate, potassium chloride, sodium and magnesium chlorides, 

 have all given positive results in this direction, and it is probable 

 that these substances contain the elements needed by the weak- 

 ened protoplasm. We are justified, therefore, in regarding the 

 artificial rejuvenation of Parainccciuin as a phenomenon of the 

 same order as the chemical fertilization of the egg. 1 



The general problem may be attacked from another point of 

 view. What is it that conjugation does to renew the potential 

 of vitality ? The early conception of Butschli's that conjugation 

 brings about a renewal of youth or a Verjungung of the partici- 

 pating organisms has been repeatedly confirmed by subsequent 

 observers. A very significant fact came to light in the course of 

 these experiments and one which seems to show that conjugation, 

 like the action of the beef-extract, involves certain chemical phe- 

 nomena. It will be recalled that Maupas maintained that endog- 

 amous conjugation is fruitless and the reason given was that, as 

 the cultures grow older, the micronucleus degenerates and dis- 

 appears. Maupas did not keep Paramcecium in culture for more 

 than a few weeks, but the period was long enough for him to 

 feel justified in assuming that this form is similar to the other 

 forms examined by him. He declared that endogamous conju- 

 gations in this species (and he obtained many of them) are ster- 

 ile because the micronucleus is lost through degeneration. I 

 have preparations of this form made at intervals throughout the 

 665 generations, during endogamous and exogamous conjuga- 

 tion, at periods of depression and of vigor, and in none of them 

 is the micronucleus absent. Upon this point Maupas was most 

 assuredly mistaken. 



From time to time As and Bs have been put together for 

 the purpose of obtaining fertile conjugations. In the material 

 set aside as " stock " conjugations have also frequently occurred, 

 these of course, being endogamous. A comparison of " wild " 



1 Cf. Calkins. Studies on the Life-Cycle of Protozoa. I., The Life-Cycle of 

 Paramcediim caudatum. Arch, f. Entwickl., 1902. 



