Protozoa and Rotifera at Havana, III. 327 



44. S. uvella Ehrbg. 



This species was seen only occasionally at first, a few being 

 observed in April and a single one in July. In October and 

 November it became common in the river towings, and from 

 December to March was more or less abundant at all the sub- 

 stations under examination, reaching its maximum in Janu- 

 ary. 



Family VOLVOCIDiE. 



Pandorina Bory. 



Colonies free-swimming, spherical to oval, consisting usu- 

 ally of 16, rarely 32, individuals closely joined at a common 

 center. 



45. P. morum Bory. 



Observed only during the second year's work, from April 

 to September, and again from January to March. It was 

 quite common, but was not found in Phelps Lake. This spe- 

 cies forms an important element in the food of large rotifers. 



Volvox Linn. 



Colonies spherical, large, consisting of many thousand 

 similar zooids forming an enclosing wall about a large cen- 

 tral gelatinous mass. 



46. V. globator Linn. 



Abundant and well distributed in the field studied, except 

 in Phelps Lake, where it was only seen once. In midwinter 

 it became rare. It was abundant near the field laboratory in 

 Quiver Lake during July, and though many were taken here 

 in the bottom towings, none appeared in the surface towings 

 made during the day. 



Pleodorina Shaw. 



Colonies more or less oval, consisting of about 128 individ- 

 uals of two kinds, the large ones about one polo and the 

 small ones about the other, enclosing a central gelatinous 

 mass. 



