454 Gary N. Calkins. 



Wilson in The Cell attributes to O. Hertwig, that the condition of 

 stabiHty is changed into one of protoplasmic lability. 



While such an hypothesis accounts for the first two periods of 

 depression, it fails to account for that of June and of December, 

 1902. In the interval between June and the preceding December, 

 the race in part, had been treated weekly with beef extract until 

 the first of April, after which the organisms had been fed with the 

 usual hay infusion. In June they began to degenerate, and from 

 this time on, treatment with the beef extract was futile, and the 

 race was finally saved only by using extract of pancreas and of 

 brain. This, however, gave only temporary relief and complete 

 activity was never again recovered and the division rate remained 

 below the average, until the race finally became extinct in Decem- 

 ber, 1902, and this despite the fact that, morphologically, the 

 endoplasm and macronucleus were restored. 



Was the last period of depression running from June until 

 December, 1902, an expression of old age ? From the structures 

 of the organism and their behavior, there is no doubt that the 

 ailment at this period was different from that of the earlier 

 periods of depression, and there is no doubt again that the reme- 

 dies which had succeeded at the earlier periods failed completely 

 at this. The final depression of vital activities may be accounted 

 for by one of two assumptions : (i) There was an accumulation of 

 waste material of a different kind from that of the earlier periods, 

 or a different physical condition, and a weakening of different 

 functions, or (2) certain elements in the protoplasm endowed with 

 a given potential of activity used up that potential and failed to 

 recover it by artificial stimulation. Or a third hypothesis may be 

 conceived which embodies both of these. The morphological 

 structure at the final period shows that some different elements of 

 the body were involved in the last period of depression, and that 

 the elements which had given out in the previous periods were 

 satisfactorily reinvigorated even in the last individuals of the 

 race. Thus the micronucleus and the cortical plasm showed 

 unmistakable signs of degeneration in the last few individuals of 

 the race, while the endoplasm and macronucleus were perfectly 

 normal in appearance, and metabolism, which these elements of 



