BENEATH TROPIC SEAS 



appropriate cases. It is now altogether superceded 

 by preparations of iodine. " 



So when in diving helmet we walk on reefs, and 

 pluck sponges of all colors and sizes, and come to 

 the surface with our fingers black and brown with 

 iodine, we remember the old specific. Sea-weeds 

 which are counted rich in iodine contain only about 

 one and a half per cent, while some of our sponges 

 possess as much as fourteen per cent, or almost one- 

 seventh of their entire being. The big sage-green, 

 chimney sponges begin to turn black and to darken 

 the water as soon as they are put in an aquarium. 



As we have seen, an active, excited sponge has, 

 in the matter of movement, little advantage over 

 a bit of moss, and yet an infant sponge, swirled 

 out upon the current of the parent cave-mouth 

 may found a new colony half a thousand miles 

 away. 



The eggs begin their development deep within 

 the jelly-like tissues of the parent sponge, and one 

 day, in company with unnumbered hosts of its 

 fellow brood, an embryo works itself free, whirls 

 around and around, and shoots out of the exhalent 

 pore into the world of ocean. It looks like an 

 infant balloon, the upper half of large, smooth 

 cells, while those of the lower half each bear a long 

 tail or flagellum which beats frantically upon the 

 water. There is no unison or rhvthm, — each lash 

 whips out at its own sweet will, but they do man- 

 age to beat more strongly in a backward direction, 

 and thus the balloon forges ahead. The light 



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