130 PROTOPLASMIC AGE OF PROTOZOA 



the approach of disintegration. The papillae of the cuticle were plainly 

 visible, and what I have taken to be apertures of the trichocysts 

 were more or less numerous. (This is shown in the preserved cell, 

 Fig. 54.) A few trichocysts remained in the cortical plasm, but there 

 were many vacuoles in this layer, indicating that when the trichocysts 

 were discharged they were not reformed. The peristome was normal 

 and the mouth had a vigorous oral membrane. The size was large, 

 fully as great as any of the preparations that had been made at any 

 time during the 742 generations. Movements vigorous to slow, with 

 a tendency on the part of the animal to remain stationary.' 1 



'It was while the organisms were in this structural condition that 

 the many attempts to rejuvenate the race were made as described in 

 the previous pages, and it was in this condition of the protoplasm that 

 the race finally died out from exhaustion. Before dying, however, the 

 individuals, as indicated in the above paragraph from my notes, were 

 of full size and were filled with gastric vacuoles and partly digested 

 food, while the body form was normal. 



"It must be admitted that these forms ivere capable of individual 

 growth at this period, and since the macronucleus was norm<d in the last 

 individuals, while the micronucleus was considerably changed, it must 

 be further admitted that the vegetative metabolic processes were presum- 

 ably re-invigorated; on the other hand, the functions of reproduction, 

 that is, of division, were degenerated possibly, if not probabhj, because 

 of the apparent degeneration of the micronucleus and of the cortical 

 plasm, whose functions were not reinvigorated by the artificial means 

 which were tried." 



We are not in a position yet to demonstrate the nature of the cause 

 of the depression periods. It is probably to be sought in the chemical 

 make-up of the constituents of the cell, the chemical changes necessary 

 for the functions of digestion, such as the formation of proteolytic 

 ferments, oxidizing ferments, and the like, being no longer possible 

 with the same food. We may compare a paramecium or oxytricha 

 with a storage battery, the one having, at the outset, a certain potential 

 of physiological activity, comparable with the initial electric charge 

 of the battery. With the same food for a period of six months the 

 initial charge of vitality is drawn upon, as work done draws upon the 

 initial potential of the battery, until in a period of depression the 

 resources of the cell are exhausted and the organism dies by what 

 Hertwig calls "physiological" death. 



The battery, however, to continue our analogy, can be recharged 

 and is good for another period of work. So can the paramecium pro- 

 toplasm. The six months of culture does not exhaust the germinal 

 possibilities of that protoplasm; in the cultures referred to, the organ- 



1 From my notebook. 



