160 BROOKLYN BOTANIC GARDEN MEMOIRS 
torial series, while the four coming from the peripheral four cells of the 
eight-celled stage (Text-fig. 2) form a new polar group of four whose 
cells alternate with those of the original polar group. Henfrey (’56) 
described the sixteen-celled colony of Eudorina as consisting of two 
polar groups of four and an equatorial circle of eight cells. 
Biitschli (’83) describes the sixteen-celled colony as consisting of 
four upper central cells, a ring of eight equatorial cells and four lower 
cells which alternate with the upper and gives a figure (Taf. XLV, 
Fig. 1, 7). Overton’s (’89) description of the arrangement of the 
cells in the eight-celled stage is essentially like that of Biitschhy, 
though as Meyer notes, he ascribes the origin of the central cavity 
of the colony to the divergence of the cells in the four-celled stage 
and the subsequent hollowing out of the cells toward the center of the 
I 
tN 
Fics. I AND 2. For explanation see text. 
colony. Neither of these authors gives any very clear account of the 
arrangement of the eight equatorial cells or their relationship to the 
polar groups. 
It is not easy to obtain satisfactory photographs of these sixteen- 
celled stages since, as noted, they are practically spherical and the 
number of cells is so small that no characteristic groups can be ob- 
tained in one focus. From a study of a large number of cases and 
photographs of various views I have been able to obtain data for the 
model made of marbles held together with wax and shown in two views 
in text-figures I and 2. Text-figure I shows the anterior pole of the young 
colony with the four cells forming a square, as has been observed by 
all students of the group. The opposite posterior pole of the colony 
would show a similar group of four, each cell alternating with the 
four at the posterior pole. 
