452 Gary N. Calkins. 



sticky or plastic and to such an extent that two individuals upon 

 meeting, fuse together in plastogamy. This, which I have 

 termed elsewhere the "miscible state," may be so marked that 

 groups consisting often of from five to eight aggregated individuals 

 are occasionally seen. It is analogous, apparently, to the plas- 

 togamy so often seen in the fresh water testacea such as Diffliigia 

 or Arcella, which Schaudinn has recently shown to have no 

 connection with conjugation in these instances. In Paramcecium 

 during this miscible state, conjugations are for the only times 

 possible, and many complete conjugations are found together 

 with the fused multiple individuals. There is no doubt, then, that 

 the cortical plasm changes in physical condition, and there is equal 

 reason to believe that at periods of depression when these abnormal 

 divisions are more frequent, the cortical plasm shows degenerate 

 conditions^ or, possibly, a condition of old age. 



There is therefore some significance in the fact that the cortical 

 plasm gives out; some significance connected with the diminishing 

 division rate and with advancing old age as evidenced by dimin- 

 ishing activity. 



While there may be some uncertainty as to whether the decreas- 

 ing vitality of a race of Paramcecium is evidence of normally 

 decreasing functions indicative of protoplasmic old age, or of 

 some other cause of degeneration, there is absolutely no reason to 

 believe that it is due to a parasite of any kind, nor to any harmful 

 substances in the medium in which they live. In the earlier 

 periods of depression there seems to have been a gradual loss of 

 powers connected with metabolism, and of something which was 

 vitally important to the race, for unless the individuals were stimu- 

 lated, they inevitably died. This was strikingly demonstrated in 

 the period of depression in December, 1901, when a number of 

 individuals of the regular series were continued on the usual hay 

 infusion, while others were treated with beef extract for 24 hours, 

 and still others with salts of different kinds for not more than 30 

 minutes. The non-stimulated forms showed increasing sluggish- 

 ness and depression, and all died in the course of two weeks, while 

 the sister-cells which had been stimulated, lived with varying 

 fortunes until a year from then (see Diagram I). The pertinent 



