6o6 Lorande Loss Woodruff. 



stimuli, and he found that an extract of beef, among others, was 

 most effectual. As previously stated, I employed beef-extract 

 as a stimulant during the first depression period of the Oxytricha 

 A-culture which was at its height in May, 1902, and in July, 

 1902, after a latent period of about six weeks, one series suddenly 

 sprang into new life. It is certain that something "rejuvenated" 

 the culture at this time and I have every reason to believe that it 

 was brought about by the salts of the beef-extract, and that we 

 have here a case of stimulation analogous to "artificial partheno- 

 genesis" as Calkins suggests in his Paramcecium work. 



J. Conjugation. 



My endeavor to study the effect of conjugation on the life- 

 cycle of Oxytricha fallax, Pleurotricha lanceolata, and Gas- 

 trostyla steinii has been in vain, as at no time during the life of 

 any of the five cultures have I succeeded in getting a single 

 syzygy. Numerous individuals from the A and B cultures were 

 placed together at different times in an endeavor to get exogamous 

 conjugations, but to no purpose. The same is true of endoga- 

 mous conjugations. With Maupas's conditions of conjugation in 

 mind attention has been paid to the amount of food present but 

 without result. 



It seems rather remarkable that Oxytricha should pass through 

 860 generations, Pleurotricha through 448 generations, and Gastro- 

 styla through 288 generations and at no time show any tendency 

 to conjugate. The significance of this is rather difficult to see. 

 Joukowsky, however, found no conjugations in his long culture 

 of Pleurotricha, and Maupas secured none in his cultures of 

 Stylonychia mytilus or Oxytricha sp. though his other series 

 yielded plenty of syzygies. It is not uncommon to find hypo- 

 trichous forms conjugating in wild cultures in the laboratory, so 

 that it is evident that some condition must prevail there which 

 does not obtain in the experiments, and it is just possible that an 

 excess of carbon dioxid and other noxious gases in these wild cul- 

 tures may be the provoking cause ; but it seems more probable, since 

 the physical state of the protoplasm of the infusorian undoubtedly 

 plays an important role in the conjugating process, that the 

 required "miscible state" is prevented in artificial cultures through 

 the scarcity of certain salts in the liquid medium used. In the 



