VARIETIES OF ACALEPEkE. 207 



be invisible to the naked eye, and can only be 

 seen by the aid of the microscope ; others have 

 a diameter of two or three feet. The forms 

 of some are hemispherical, of others orbicular. 

 Some are seen adorned with long tentacula, 

 which stream behind them in the water ; others 

 again have no such appendages. Their mode 

 of locomotion is also various. By means of 

 contracting its disk, one species propels itself 

 through the water ; by aid of small paddles placed 

 on the circumference of the disk, another species 

 urges its way onward. They differ also in colour. 

 Some are singularly beautiful, exhibiting those 

 symmetrical patterns produced by the kaleido- 

 scope ; some are brown in the centre, with sixteen 

 lines pointing like radii to the circumference; 

 some have a light purple cross in the middle, 

 between each bar of which is a horseshoe mark 

 of a similar, though much deeper, hue, and from 

 the circumference diverge rays of the same tint, 

 but lighter than the rest. Others again have a 

 white cross, with a black spot on each of its arms, 

 and others have a disk almost as translucent as 

 the water in which they float, but in its centre is 

 a bright crimson spot, like a piece of cornelian 

 encased in crystal. The hues of others are still 

 more beautiful, though they are extremely mi- 

 nute. Of one of these last, whose tints are white 

 and crimson, the late ever-to-be-lamented Pro- 

 fessor Forbes thus elegantly speaks : " There is 

 not a medusa in all the ocean which can match 

 for beauty with the minute creature now before 



