220 The Ottawa Naturalist. 



Stephanoceros — A Beautiful Rotifer Recorded at 

 Ottawa. 



By Walter S. Odell, Esquire. 



I am not aware that the species of Rotifer Stephanoceros 

 Eichornii has been found in this locaHty, if so it has not been 

 described in the " NatuiaHst." Dr. A. C. Stokes, who is perhaps 

 the best authority on Infusoria in America, says it "does not seem 

 to be common." It has never been my good fortune to find it 

 till it appeared in my aquarium this winter, on a leaf of Cerato- 

 phyllum. Three specimens have since appeared in the same. 

 This is one of the most beautiful living microscopic objects found 

 in fresh water, and is barely visible to the eye, being 1.82 mm. 

 long, 212 mm. wide. This rotifer unlike the common forms, lacks 

 the wheel-like cilia surrounding the rim of the head, but instead) 

 five long elliptical arms arranged equidistantly on the head, are 

 held aloft like graceful plumes. These, thicker at the base, are 

 beautifully curved and extended, while the rotifer is feeding, 

 and the tips all point inwards to a common centre. Each arm is 

 bordered by a row of long hairs or cilia springing from the sides 

 and curved outwards and upwards, with inner rows of shorter 

 cilia, forming a firm cage for holding any unlucky infusorian that 

 wanders in. I have seen a Paramecium passing through this cage 

 several times without being secured. When touching the mouth 

 at the base of the arms, it was suddenly drawn, in and in few 

 seconds the creature was transformed into a shapeless mass. The 

 rotifer then straightened the arms till they appeared as a round 

 bundle of erect plumes, and gradually retracted into its case, first 

 withdrawing the head and th^n the bundle of plumes till it was 

 entirely enclosed. This hyaline case is hollow, tubular, faintly 

 ringed and about four times as long as broad, rounded at the 

 top, and constricted so as to enclose the animal tightly as if in the 

 mouth of a sac The body is pyriform, the lower part gradually 

 tapering to an attenuated foot. The mouth at the base of the 

 arms is ciliated and leads through a short passage to the mastax 

 or jaws. No eyes were present, and I would therefore conclude 



