1 V" 1 BRUCE D. KKVXOLDS. 



severed pseudopods, but upon making contact the involved pro- 

 toplasms will be shattered into bead-like masses. 



5. When two lines of a clone are kept under similar environ- 

 ments, cross-fusions between them cease after approximately 22 

 days; while if the two diverging lines are subjected to different 

 environments, the time required for cross-fusions to cease is 

 greatly shortened (varying from 6 to 16.5 days depending on the 

 factor employed). 



6. When small quantities of culture media are frequently 

 exchanged between the concavities in which members of two 

 diverging lines are confined, cross-fusions between them appar- 

 ently continue indefinitely 



7. After two related specimens have become negative to each 

 other's protoplasm, cross-fusions between their progeny may be 

 induced by (a) exchanging small quantities of culture media 

 between the receptacles in which they are kept (time required was 

 20 days), or (6) by placing both of them in the same concavity 

 (time required was 6 days). 



8. Morphological differences are not necessarily associated 

 with different physiological states, as evidenced by the fact that 

 abnormal specimens could be induced to fuse with fragments of 

 normal individuals and vice versa. 



9. Physiological changes do occur among the descendants of a 

 single A. polypora reproducing vegetatively, but such differences 

 are probably due to environmental influences rather than to 

 hereditary variations. 



BIBLIOGRAPHY. 

 Ackert, J. 



'16 On the Effect of Selection in Paramecium. Genetics, Vol. 1.387-405. 

 Barber, M. A. 



'07 On Heredity in Certain Microorganisms. Kansas University Science, Bui. 



4. 3-47- 

 Calkins, G. N. 



'n Regeneration and Cell Division in Uronychia. Jour. Exp. Zool., Vol. 10, 



95-116. 

 Calkins, G. N., and Gregory, L. H. 



'13 Variations in the Progeny of a Single Ex-conjugant of Paramecium canda- 



Intn. Jour. Exp. Zool., Vol. 15, 467-525. 

 Castle, W. E. 



'14 Pure Lines and Selection. Jour. Heredity, Vol. 5, 93-97. 

 Erdmann, Rh. 



'20 Endomixis and Size Variations in Pure-bred Lines of Paramecium aitrelia. 

 Arch. f. Entwicklungsmech., Bd. 46, 85-146. 



