NEREIS NOCTILUCA. 325 



flashes are emitted ; and should different parts of the 

 sides of the vivarium be occupied by several speci- 

 mens, as is always the case where miscellaneous col- 

 lections have been recently introduced, so many bril- 

 liant coruscations will escape from all the parts of the 

 vessel where they are established. This interesting, 

 though rude experiment, may be repeated several times 

 upon the same subjects; however, if these are to be 

 preserved, the vessel must be speedily drained and 

 refilled with their proper element, as few marine ani- 

 mals can survive even a short immersion in fresh water. 

 The Nereis noctiluca is at all times an elegant and 

 instructive little creature, serving at least to show 

 what various forms of life Nature has lighted up to 

 beautify the deep, 



" Or gild the surge with insect sparks that swarm 

 Round the bright oar." 



We have yet to discuss one of the most interest- 

 ing departments connected with the history of the 

 Nereides, namely the metamorphoses which these 

 creatures undergo after leaving the egg, and their 

 subsequent growth to their mature condition, sub- 

 jects which, to every aquariist, present a rich field 

 for observation and research. 



We need hardly say, that the Nereis, in the earlier 

 stages of its growth, does not as yet possess the 

 almost countless segments that it afterwards acquires ; 

 and yet the mode in which those segments become 

 multiplied, and, as they grow, provided with the com- 

 plicated limbs they sometimes bear, was, until re- 

 cently, a most unfathomable mystery. 



The Nereis, when it leaves the egg, is quite a limb- 



