346 SEA-SIDE STUDIES. 



irritant, no matter of what nature, produces this phos- 

 phorescence in them. The phenomenon is not, as in 

 insects, one of combustion ; but is intimately con- 

 nected with the contraction, spontaneous or provoked, 

 of their substance. It is independent of all secretion, 

 and it is probable that the sparks are due to the 

 rupture and sudden contraction of their sarcodic fila- 

 ments ; while the steady light they emit in dying, 

 results from the permanent contraction of this sarcodic 

 substance. 



Having satisfied curiosity about the Noctilucce, let 

 us turn once more to the Gydippes, which should be 

 placed in the tallest jars, because, while the Medusae 

 keep at the surface, where they swim with successive 

 pants, the Cydippes constantly let themselves drop to 

 the bottom, and rise the next moment in graceful 

 buoyancy, drawing their graceful streamers after them, 

 these streamers elongating as they ascend, until from 

 shrivelled threads they unfold into long and graceful 

 forms, which, on coming into contact with any object, 

 shrink rapidly again into their former shrivelled con- 

 dition. All this while the locomotive paddles of cilia 

 sway the animal with restless grace — a charming 

 sjDectacle ! After admiring it abundantly, you may 

 commence a closer inspection of the creature's struc- 

 ture, which is sufficiently curious, but need not detain 

 us here, because you may see in any text-book what 

 is known, and I know nothing more than what is 

 there recorded. One remark only need be made : the 

 notion of the streamers (or tentacles) being locomo- 



