140 EEMINISCENCES OF 



The grandest of these is the beroe. In size and form 

 it precisely resembles a purse, the mouth, or orifice, an- 

 swering to one of the modern metallic clasps. It is 

 perfectly transparent, and in order to distinguish its 

 filmy outlines, it is necessary to place it in a tumbler of 

 brine held between the observer and the light. In cer- 

 tain directions the whole body appears faintly irrides- 

 cent, but there are several longitudinal narrow lines 

 which reflect the full rich tints of the rainbow in the 

 most vivid manner, for ever varying and mingling the 

 hues, even while the animal remains at rest. Under 

 the microscope these lines display a succession of innu- 

 merable coloured scales or minute fins, which are kept 

 unceasingly in motion, thus producing the play of co- 

 lours by continually changing the angle of reflection. 



The movements of the beroe are generally retrograde, 

 and are not aided by the coloured scales, but depend 

 upon the alternate contraction and dilatation of the 

 mouth. The lips are never perfectly closed, and the 

 little fish and shrimps which play around them are con- 

 tinually entering and leaving them at pleasure. The 

 animal is dependent for its food upon such semi-anima- 

 ted substances as it draws within its grasp by moving 

 slowly backwards in the water, and retains them in con- 

 sequence of their own feebleness and inability to escape 

 the weakest of snares. 



Another tribe of the sea-purses, (salpa,) though much 

 smaller than the beroe, are more complex in structure, 



