58 



Scientific Proceedings (97). 



died and nine are still under observation in different stages of 

 vitality. 



Theprocessof parthenogenesis ("endomixis" of Woodruff and 

 Erdmann) occurs in Uroleptus while encysted. These cysts re- 

 quire drying before the individuals will emerge. Parthenogenesis, 

 therefore, is too clearly advertised to be overlooked, and the 

 effects of such asexual reorganization cannot confuse the results 

 obtained by the isolation cultures, for, while parthenogenesis 

 occurs in the conjugation tests, it never has occurred in the iso- 

 lation cultures. 



In these experiments we deal with one protoplasm originally 

 contained in the single-celled ex-conjugant of the A series. Some 

 of this protoplasm has been maintained in isolation cultures 

 where conjugation and pathenogenesis have been prevented; 

 some is represented by protoplasm that has passed through pro- 

 cesses of conjugation, both closely-related individuals in all cases 

 being of the same age and having had the same identical treat- 

 ment daily and with the same standardized food as the protoplasm 

 of the parent isolation cultures; and some is represented by indi- 

 viduals that have passed through the processes of encystment and 

 parthenogenesis. 



The problems presented are: (1) Does the protoplasm of an 

 ex-conjugant and its progeny by division, undergo progressive 

 weakening of metabolic vigor ending in natural death? (2) Does 

 conjugation between two individuals of the same age and each 

 composed of similar, weakened protoplasm, result in the restora- 

 tion of metabolic vigor to an optimum? The results of the exper- 

 iments prove clearly, that both questions, so far as Uroleptus is 

 concerned, are answered in the affirmative. 



First, as regards physiological weakening and natural death. 

 The original A series died in the 313th generation. The B series 

 (obtained from a cyst) died in the 258th generation. The C series 

 (from A 78) died in the 349th. The D series (from A137) died 

 in the 271st. The F series (from C 86) died in the 317th. The 

 G series (from B 115) died in the 291st, and the H series (from 

 A 237) died in the 268th generation. All of the other series are 

 still living, although two of them (I and J) will be dead within a 

 month. 



