Pleodorina, a new genus of the Volvocinez.' 
WALTER R. SHAW. 
WITH PLATE XXVII. 
In September, 1893, the writer collected at Palo Alto, 
California, a Volvox-like alga, which Dr. D. H. Campbell at 
once suggested was different from any described genus. 
Subsequent review of available literature on the subject at 
Stanford University and by Dr. W. G. Farlow and Mr. B. M. 
Davis at Harvard University, brings to light no mention of a 
similar form. The plant is a so-called ‘‘ccerfobium” of about 
128 biciliate cells, one-half to two-thirds of which are, in the 
non-sexual form observed, ‘‘parthenogonidia.” In view of 
its apparent affinity with Pandorina and Eudorina, the larger 
number of cells, and the differentiation of the cells into two 
kinds, the name Pleodorina seemed appropriate and was 
adopted. 
The first specimens were collected Sept. 19, 1893, in an ir- 
tigation ditch at Palo Alto, and others were taken from the 
same place at intervals of a few days for about two weeks. 
They were kept in a wide bell-jar until Oct. 13th, when they 
suddenly disappeared before a swarm of insect larve. The 
living specimens from which drawings were made were held 
in place under the microscope by allowing the cover-glass to 
Press upon them slightly. An attempt was made to deter- 
mine the time required for the full development of the goni- 
dium-bearing individual from the gonidium by isolating ma- 
ture plants in watch glasses; but the daughter plants were 
not healthy, and did not come to maturity. 
€ typical specimens are those in which the gonidia have 
reached their full size previous to division. Such individuals 
are spherical (fig. 1) or more often ellipsoidal, and measure 
2 7-258 in long diameter;? the short diameters of ellipsoidal 
Specimens measure 7-20 less. With one exception the num- 
ber of cells in those counted varied from ninety-eight to one 
hundred and twenty-six; the exception numbered sixty-three 
Prepared under the di i bell 
. e direction of Dr. Douglas Houghton Campbell. 
nee of the measurements and also the counts of the cells given ae a 
Staining Specimens permanently mounted in 25% glycerine after fixin 
