SUBTERRANEAN LIGHT-GIVERS. 37 



glass in a dark room, — the little bags, seemingly at a white 

 heat, darting about in every direction. 



As small as are these wonderful creatures, they are well 

 worthy of study ; and even those not interested in natural 

 history will find that the stems of their flowers, or the water 

 in the vase, contain more wonders than they had dreamed 

 of, — a single drop that can be lifted upon a pin-head being 

 sufficient for the purpose. 



The little hat-like form, Hydatina senta, already referred 

 to, is remarkable for the rapidity of its increase. The eggs 

 are laid or deposited within a few hours of the time they are 

 first seen within the transparent parent, and twelve hours 

 later the young break from the shell and appear ; so that in 

 a comparatively few days the descendants of a single animal 

 might possibly far exceed the population of the United. 

 States. The larger worms are with hardly any exception 

 ornamented in some remarkable way, and in many the splen- 

 dors of their decorations must be seen to be appreciated. 

 The radiating coronets of Ser'pulce ^ are of the most delicate 

 and beautiful description, abounding in bands and markings 

 of striking hues. Pectinaria has upon its head a pair of 

 combs that might be burnished gold ; while Eunicedce and 

 NereidcB ^^ have equally resplendent decorations. 



These charms of color, and they are of great variety, are 

 seen by day ; but at night many of these creatures assume 

 the gift of phosphorescence, adding to the long list of marine 

 light-givers that have been previously referred to. In foui' 

 other families ^ are found the most beautiful light-givers of 

 the group. Assuming that we have a certain species of the 

 first mentioned in the aquarium, we may prepare for an 

 extraordinary display. It is now suugJy coiled up under a 



