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. I, i). Overton's ('89) description of the arrangement of the 

 cells in the eight-celled stage is essentially like that of Biitschli, 

 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 2 



Figs, 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. 



