PERIODIC REORGANIZATION IN PARAMAECIUM 489 



deleterious bacterial strain. Some types of bacteria produce 

 unhealthy conditions which are readily recognizable when one 

 has conducted a culture for a long time and consequently, when 

 such appear, they can be eliminated. Now and then, however, 

 a culture becomes contaminated with a form which does not 

 produce a characteristic change in the medium and therefore it 

 is not noticed. As a result, at the daily isolations, the fresh 

 medium becomes infected. This was the case with Line VI of 

 Sub-culture IE, as already described (cf. p. 467). The Infusoria, 

 then, can and do degenerate and die as a result of unfavorable 

 conditions, but we wish to reiterate that even under such con- 

 ditions the cell sometimes attempts to restore its normal equi- 

 librium by the inherent reorganization phenomenon. 



It is clear that the cycle emphasized by Maupas, Calkins and 

 others is merely a phantom which has continually receded as 

 each successive investigator has approached the problem with 

 improved culture methods until it has vanished with Woodruff's 

 race of (so far) 4500 generations. What remains then is the 

 rhythm and in the light of the present study, which demonstrates 

 the underlying cytological phenomena of which it is an outward 

 physiological expression, the whole problem takes on a new aspect. 

 The cell automatically reorganizes itself periodically by a process 

 which, in its main features, simulates conjugation — but without 

 a contribution of nuclear material from another cell. Therefore 

 it is evident (as has been shown by this culture) that the forma- 

 tion of a syncaryon, whose components are derived from two 

 cells, is not necessary for the continued life of the cell — it has 

 an internal regulating phenomenon which is entirely adequate 

 to keep it indefinitely in a perfectly normal condition. 



VIII. ENDOMIXIS AXD ITS RELATION TO CONJUGATION 



It is necessary now to consider the significance of the reorgan- • 

 ization process in relation to conjugation in which the formation 

 of a syncaryon results in a union of chromatin from two distinct 

 animals. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 17, NO. 4 



