STENTOR. 63 



shape. Its scientific name is Stentor. It is very common in ponds 

 and ditches, forming more or less extended colonies on the surface 

 of the stems of water-weeds, or submerged sticks and stones. 

 Some of the varieties, for they can hardly be called species, have 

 a deep ccerulean blue color, and on this account their presence 

 is readily detected by the sudden shrinking of blue patches of 

 what appears to be a sort of blue mould, when they are touched, 

 or the stem to which they are attached is shaken. The fully ex- 

 panded variety, which I have figured here, is perfectly colorless, 

 and constructs a distinct tube (sh) of gelatinous matter, into 

 which it retreats, when disturbed, and shrinks into a globular 

 mass. Its narrower end (a) is attached to the bottom of its 

 sheath at the will of the animal ; and although it seems rarely to 

 leave its domicile, yet when it does so it has the power to 

 detach itself without violence, and 

 move away to any other spot, and 

 there affix itself again and build ""' 



n| 



up a new tube. The most striking 

 | feature about this animal is the one- 

 sidedness of its figure, as if the edge 

 of the mouth of the trumpet had been 

 cut off obliquely, and the rim stretched 

 Fig. 3-2, out at one point. On the side next 

 the observer's eye the edge turns inward (at m) so Fig. 33 - 



Fig. 31. Stentor polymorphus. Elir. 100 diam. A much larger specimen 

 than fig. 30, from the same point of view, undergoing the process of fissigemma- 

 tion, whilst swimming about in a half expanded state, c, the head or disc of the 

 original stock ; a 1 , the point of separation, which is at the tail of the old stock and 

 the right side of the head c 1 of the new individual ; m, mouth ; m 1 , throat; ?w 2 , 

 posterior end of the throat ; c, ciliated edge of the disc ; c 1 , the as yet incom- 

 plete ciliated edge of the disc ; cv, the contractile vesicle in the distance ; cv 1 , 

 cv 2 , the posterior tubular prolongation of cv ; n, n l , n' 2 , the reproductive organ, 

 more or less swollen from point to point by the enlarging eggs; s, the disc of the 

 new individual, about three quarters enclosed by the ciliated margin c 1 . 

 Original. 



Fig. 32. o, the same as fig. 31, whilst attached and fully expanded; b, a 

 single individual with its posterior end partially coiled. 8 diam. Original. 

 Fig. 33. The same as fig. 31, seen from the opposite side or back. 50 diam. 



