45 o Gary N . Calkins. 



plasm and micronucleus show evidences of degeneration, all of the 

 experiments that we may try to artificially reinvigorate them, 

 will probably be futile. This may indicate one of two things, 

 viz: that under natural conditions changes m immediate environ- 

 ment would be insufficient to rejuvenate when the organisms are 

 in this ultimate state of exhaustion, unless, indeed, the experi- 

 ments failed to eliminate all of the chances such an organism bas- 

 in nature; or, conjugation is a necessary condition of continued 

 protoplasmic activ.ty. 



I am inclined to the belief that some material might ultimately 

 have been found which would have helped the Paramoecia over 

 this period of extremity and would have stimulated micronucleus 

 and cortical plasm to continued work. The failure to find it, 

 however, indicates a like difficulty in nature and makes the 

 a priori reason most probable that the phenomena with which we 

 are familiar, namely, the processes of conjugation, have been 

 essential in mamtaming the races of Paramecium up to the pres- 

 ent time, and in keeping them from extinction. 



2. Does Protoplasm Grozu Old? 



The above considerations lead to the discussion of age in a 

 simple cell organism. In higher forms old age is manifested by 

 the gradual weakening of the vital functions, waste matters are 

 inadequately disposed of, or are retained in one form or another 

 in the cells and tissues; this involves the physical impairment of 

 organs and enhances the difficulties of their functional activities 

 until, by the accumulation of such mutually aggravating processes, 

 the organism ultimately dies of "old age." In Paramcectum 

 there is little morphological evidence of the onset of old age, 

 although, if we accept the impairment of the vital functions as an 

 index, we must conclude that diminution of the division rate, 

 decrease in size, etc., are evidences of this phenomenon in pro- 

 tozoa. So far as the accumulation of waste matters is concerned, 

 there is morphological evidence to indicate that this takes place 

 more frequently at periods of depression. There was no sign of the 

 crystals which frequently accumulate in the protoplasm of various 

 protozoa, and in the last specimens of the race (742d generation) 

 both endoplasm and macronucleus were normal in structure. 



