84 Dwellers of the Sea and Shore 



start out in life as a spherical swimming egg, called a 

 planiila, and later become branching hydroid colonies; 

 in other species, neither the colonial nor the strobila 

 stage marks their metamorphosis; they pass without 

 alternation of generation directly into the ephyrula 

 state. 



Notwithstanding that many of the comb jellies and 

 jellyfishes are luminous, they are not essentially crea- 

 tures of the night. It is true that some species among 

 the latter never liberate their eggs until after the sun 

 has set; however, it is equally certain their eating habits 

 are not regulated by the sidereal alternation of daylight 

 and darkness. Yet it is the night that reveals them in 

 their most peculiar splendor. If by day the witchery 

 of these resplendent forms is overwhelming, what shall 

 we think of them at night when the fulgor of their mys- 

 terious lanterns flashes forth in the inky depths like 

 pale-blue comets or streaks past with the similitude of 

 shooting stars in the moving tide? 



In general it may be said that little is known about 

 the nature of animal light, and the luminous property 

 of coelenterates in particular is still an obscure subject. 

 Indeed, even the life histories of only a few jellyfishes 

 themselves are completely understood. One who would 

 aspire to explore in a most interesting and an undevel- 

 oped field cannot do better than to give his attention 

 to the coelenterates, a group whose members easily rank 

 among the most beautiful of all the living wonders. 



