No. 3.] MORPHOLOGY OF THE STENTORS. 473 



so far as I have observed, have a single nucleus ; the majority 

 have two, and many from three to five. Only once have I 

 observed six. Stein ('67, p. 263) sometimes found three nuclei, 

 but never a larger number. 



I a. Stejitor igneus var. jiigricans, var. nov. 

 (Fig. i; PI. XXIII.) 



In a little pond at Williamstown, Mass., I found countless 

 numbers of a small Stentor, which seemed so different from all 

 known species that for a long time I regarded it as new. The 

 pond filled a slight depression in the open fields, covering about 

 half-an-acre. It contained a scanty growth of aquatic o-rasses 

 and rushes, but hardly any other vegetation. The Stentors 

 were collected at various times during the fall of 1890 up to the 

 time of freezing, and a few were kept in the laboratory through 

 the winter. In the following April they were again obtained, 

 at first in small numbers, but soon in the greatest abundance. 

 By the middle of May they were so numerous as to give a dark 

 coffee-color to the water of the pond, and completely cover all 

 objects beneath its surface. 



To the naked eye this form appears as a minute conical 

 body, blackish or olive-green in color. Under the microscope 

 the green tinge is seen to be due to symbiotic algae, while the 

 blackish color is produced by a minute pigment in the ecto- 

 plasm. The meganucleus is conspicuous as a single, glistenino- 

 body on the right side (Fig. i, mgn). When disturbed the 

 animals swim rapidly with the usual rotatory motion for a lono- 

 time ; but under quiet conditions attach themselves to fixed 

 objects. 



Later in the season I found at Wood's Holl the same Stentor 

 in the small "kettle-hole" pond above mentioned, livino- in 

 company with the typical .S. igncus. The ordinary individuals 

 of the two forms were so different that one could readily 

 distinguish them by the naked eye. Not only do they differ in 

 color, but also in shape and size. But after examining and 

 closely comparing large numbers, I found individuals that could 

 not be referred with certainty to cither the type or its variety 



