EUDORTNA. 159 



in a single sphere. These are supposed to be fecundated 

 oospores, originated in a female coenobium. 



Plate CLII, fig. 4, three stellate forms ; fig. 6 has one 

 included ; fig. 5, one separated from the coenobium. 



SPHAEROSIRA VOLVOX, Ehrb. 



Some authors consider this form related to Volvox; others 

 regard it as the male form ; that it is related to Volvox is 

 certain, but whether any distinct functional relation exists 

 between them has not been satisfactorily determined. 

 Probably it is merely a peculiar condition of dissolution, 

 cells enlarging somewhat after separation from the walls of 

 the coenobium. 



A form by no means rare in ponds in which the Volvox 

 prevails. It may be obtained also in vessels in which Vol- 

 vox globator is kept for cultivation. 



Plate CLI, fig. 5, a part of a coenobium of Sphaerosira 

 volvox. Description after Williamson in Cooke's British 

 Fresh-water Algw ; fig. 6, protoplasmic mass from the coeuo- 

 biurn containing granules ; fig. 7, mass divided into two ; 

 fig. 8, mass divided into four parts, and fig. 9, into thirty- 

 two parts, each with movable cilia ; fig. 10, discoid family 

 revolving in the mother sphere. 



These discoid families have come under my observation, 

 not in the sphere, but outside ; they were evidently parts of 

 a broken, or partially decayed coenobium. 



Volvox globator is distributed over the whole length and 

 breadth of the United States ; it is found in ponds and pools, 

 most abundant in warm weather, but in good condition, also 

 in midwinter. The specimens examined from many locali- 

 ties, from Maine to Florida and westward, appear to be one 

 and the same species. 



VOLVOX MINOR, Stein. 



I judge to be merely a variety of uncertain value. 



Genus 33, EUDOEINA, Ehrb. 



Coenobium somewhat ovate or spherical, involved in a more 

 or less gelatinous hyaline tegument, composed of 16-32 globose 

 green cells arranged around the colorless sphere at subequal 

 distances ; each cell furnished with two vibratile cilia pro- 

 truding through the tegument. Usually four of the thirty -two 



cells develop antheridia and others oogonia. In each antheri- 

 l] 



