46 



SUMMARY OF CUERENT RESEARCHES RELATING TO 



Protozoa. 



Protozoa of Manila. — F. G. Haughwout (Philippine Journ. Sciy 

 1918, 13, 175-214). A useful introduction to the study of the Protozoa 

 is given, including a discussion of their definition, their classification, 

 and the best ways of collecting, cultivating and mounting them. A 

 census of Philippine forms is planned. J. A. T. 



Variations in Arcella. — R. W. Hegner (Froc. Nat. Acad. Sci., 

 1918, 4, 283-8, 2 figs.). Jennings has shown that the descendants of 

 a single specimen of Dijfiugia may be separated into a number of diverse 

 lines that differ from one another in their heritable characteristics. 

 Hegner finds that within a large family of Arcella dentata produced by 







Outlines of specimens of Arcella dentata belonging to one family. 



A. The progenitor of the entire family. B. A typical member of the 

 low line E. C. A typical member of the high line A. D. The small 

 progenitor of one of the lines. E. A small specimen from one of the 

 lines. F. The largest specimen of the same line. 



vegetative reproduction from a single specimen there are many heritably 

 diverse branches. These diversities are due both to very slight 

 variations and to sudden large mutations. The formation of such 

 hereditarily diverse branches appears to be a true case of evolution 

 observed in the laboratory, and occurring in a similar fashion in natural 

 conditions. In all 6474 specimens were studied. J. A. T. 



Nuclear Re-organization in Arcella. — H. M. MacCardy {Proc. 

 Amer. Zool. Soc. in Anat Record, 1919, 15, 356-7). A given individual 

 produces a limited number of daughter-cells (0-27), which do likewise, 

 till " depression " sets in. Individuals passing successfully through this 

 may give rise to mutations or may continue the old line. Nuclear 

 reconstruction may occur during depression and during conjugation. 



J. A. T. 



