318 GEORGE \V. TAXNREUTHER. 



reported by Fermor, the macro-nucleus disintegrates and a new 

 micro-nucleus and a new macro-nucleus are formed from the old 

 micro-nucleus, thus undergoing a complete nuclear reorganization 

 comparable to conjugation. 



GENERAL SUMMARY. 



1. Prorodon griseus is a Holotrichous ciliate. It is recognized 

 by its sub-terminal oral aperature, its rod like structure enclosing 

 the pharynx, and its terminal contractile vacuole. 



2. P. griseus has a single inicronucleus and a single macro- 

 nucleus. 



3. Binary fission and conjugation occur either while encysted 

 or in the free forms. 



4. Encystment serves for protection, reproduction and re- 

 organization. 



5. Cysts are of two kinds: (a) temporary for protection during 

 short intervals. () permanent for reorganization of cell and 

 protection for long intervals, from one cycle to the next. 



6. Conjugation is terminal, fusion occurring at their anterior 

 ends. Conjugation occurs immediately after the animals escape 

 from the cysts. 



7. The aniir/als are found encysted during the greater part of 

 their life history. The greater number of free forms are found 

 immediately after conjugation, during the active feeding period. 



8. Encystment and conjugation in P. griseus have little or no 

 effect in the production of new vigor and in the change of fission 

 rate. 



9. The old macronucleus persists during early conjugation, 

 then disintegrates and disappears by absorption within the 

 cytoplasm. 



10. The new micronucleus and macronucleus are formed from 

 the daughter nuclei, produced by a single division of the conju- 

 gation nucleus. 



1 1 . The reduction of chromosomes occurs in the second 

 maturation division by a pairing of the eight chromosome in the 

 formation of the four bivalent structures. 



12. In the third division the pronuclei at first are connected by 

 a drawn out fiber. 



