6l2 Lorande Loss Woodruff. 



In the two series of Pleurotricha I have found no nuclear 

 variation at any time. Although neither of these cultures w^as 

 actually carried to natural death, still from the large number of 

 generations attained it would seem that nuclear changes should 

 have appeared if they occur in this species. Joukowsky's culture 

 of 458 generations of this species, however, gave the same result 

 and that this has been held unjustly as opposed to Maupas's 

 conclusions is evident from my cultures. A slight cytoplasmic 

 vacuolization appeared in both of my cultures as the series 

 advanced. A specimen, in a late division-stage, from the 413th 

 generation of culture B is shown in Fig. 23. 



The Gastrostyla culture showed morphological changes in the 

 form of vacuolized cytoplasm and distortion of the macronuclei 

 during the later generations; but at the time of the sudden death 

 of this series "degeneration" was by no means so marked as in 

 the Oxytricha A-culture long before death ensued. 



Briefly reviewing the chief morphological changes apparent 

 during the various cultures, we have : Oxytricha A, cytoplasmic 

 vacuolization, disappearanceof oneof the micronuclei for a period, 

 and later an increase in their number beyond the norm, distortion 

 and fragmentation of the macronuclei, degeneration of part of 

 the ciliary apparatus, and, finally, a gradual increase in the size 

 of the infusorians as degeneration advances; Oxytricha B, one of 

 the micronuclei was not present during a number of generations; 

 Pleurotricha A and B, slightly vacuolized cytoplasm; and Gas- 

 trostyla A, cytoplasmic vacuolization and distortion of the 

 macronuclei. 



Wallengren ('01) made a careful study of the morphological 

 changes which occur in starved Paramoecia, and discovered 

 that in the later stages the endoplasm is distorted by huge vacuoles 

 and finally the macronucleus is deformed and broken. The 

 micronucleus, however, remains unscathed throughout the starva- 

 tion changes. Calkins confirmed these starvation observations 

 and also found that quite similar morphological changes occur in 

 degenerating Paramoecia cultures, and he believes that the simi- 

 larity of the changes in the two cases indicates that it is the diges- 

 tive function which becomes impaired in the declining series, 

 since when in this condition the organisms still take food but 

 apparently are unable to utilize it. In my own cultures it has been 

 clear that the power of taking food is not diminished appreciably 



