474 JOHNSON. [Vol. VIII. 



nigricans. The new form must then be considered as specifi- 

 cally identical with 5. igneiis. But inasmuch as ordinary 

 specimens of the variety differ so strikingly from the type, 

 and even have in some cases a separate habitat, I consider it 

 convenient to distinguish it by name. 



Characters : Small {lejigth, extended, .204 mm., diameter 

 across frontal field, .136 mm.); form, in extension, broadly 

 cofiical or top-shaped, broadest across frontal field ; posteriorly, 

 abruptly tapering, cnrved, acute ; when stvimmi^ig and semi- 

 contracted, form conical, pear-shaped or nearly cylindrical ; 

 when fully contracted, almost spJierical. Manbratiellcs small 

 and weak ; striation of body and frontal field obscure ; minute, 

 browjtish-black pigment in the ectoplas^n ; pellicula thin, easily 

 ruptured. Contractile vacuole (Fig. i, c.v) on ventral side. 

 Meganucleus single, spJierical, ^OtJ- in diameter, usiially lying 

 near right side (Fig. i, mgn.). Symbiotic algce {ZodcJdorella) 

 ahvays observed, usually abimdant, indistinguishable fro7n those 

 of S. igneus and S. polymorphus. 



2. Stentor pyriformis, sp. nov. 

 (Figs. 2 and 3; PI. XXIII.) 



In October, 1891, I found a colony of green Stentors cover- 

 ing vegetable debris and water-weeds at the north end of Lake 

 Quinsigamond, Worcester, Mass. At first I mistook them for 

 unusually large specimens of 5. polymorpJius . But after ex- 

 tracting the chlorophyll with alcohol and staining, the mega- 

 nucleus was found to be not moniliform, but in form of two or 

 more entirely separate, spherical bodies (Fig. 3). This fact 

 led me to examine the animals with care, and various points 

 of difference between them and 5. polymorpJius were speedily 

 discovered. The new form could not fairly be identified with 

 any described species. It ranks as one of the largest of Sten- 

 tors, being scarcely inferior to S. cceruleus in size. S. pyri- 

 formis never assumes the slender trumpet-shape of the higher 

 Stentors, and in fact changes its form very little from the pear 

 or conical shape it has while swimming (Fig. 2). 



This species does not endure confinement so well as poly- 



