ZOOLOGY: KOFOID AND SWEZY 
315 
vard as far as the fourteenth magnitude. This scale intersects the Mount 
Wilson photovisual scale at the sixth and the twelfth magnitudes, but 
at other points there are important differences, some of which are ob- 
viously due to color. Further, the Yerkes Actinometry contains photo- 
visual magnitudes as far as 7.5. The Moimt Wilson results agree sat- 
isfactorily with these, and there is also good accordance with the visual 
magnitudes of Miiller and Kempf. Beyond this no results have as yet 
been pubHshed, although others are in preparation. A detailed com- 
parison with all these various investigations will be included in forth- 
coming papers in the Astrophysical Journal,^ which will also give fuller 
details and a summary of the numerical results for the Mount Wilson 
scales. The complete discussion will appear as Volume 3 of Papers 
of the Mount Wilson Solar Observatory} 
1 ML Wilson Contr. No. 80; Astrophys. 39, 307 (1914). 
^Ihid; ML Wilson Contr. No. 70; Astrophys. 38, 241 (1913). 
' Potsdam Puhl. No. 67, 
< ML Wilson Contr. Nos. 97, 98, 102; Astrophys. J. (In press.) 
* Publications of the Carnegie Institution of Washington. 
MITOSIS IN TRICHOMONAS 
By Charles Atwood Kofoid and Olive Swezy 
ZOOLOGICAL LABORATORY. UNIVERSITY OF CAUFORNIA 
Presented to the Academy, March 16, 1915 
The process of cell-division in the simpler Protozoa is significant in 
its relation to the evolution of nuclear and extra-nuclear structures. 
The behavior of the extra-nuclear organelles in unicellular organisms 
during the process of binary fission is significant as to the origin and 
relationships of such structures as flagella, blepharoplast, and axostyle. 
One of the distinctions between the CiHata and the Flagellata has been 
held to be the direction of the plane of division, transverse in the former, 
longitudinal in the latter; therefore all reported cases of transverse 
division in Flagellata should be critically inspected. 
Observations on mitosis in Trichomonas augusta, 2l flagellate parasitic 
in the digestive tract of amphibians (Diemyctylus torosus Rana boylei, 
and Bufo halophilus from CaHfornia, and Rana pipiens from Chicago) 
enable us to make a fuller correlation of mitosis in the Flagellata with 
that in the Metazoa, to correct or supplement the observations of others 
regarding mitosis in trichomonad flagellates, and to estabhsh on ample 
morphological grounds the essentially longitudinal nature of their di- 
vision. Our conclusions have been verified in all essential features, in 
