JELLY-FISHES 353 



neous colors, a fact which may be useful to you in your 

 researches, as enabling you with more ease and precision 

 to demonstrate the internal structure. 



"From the inconsiderable quantity of solid material/ 7 

 remarks this observer, "which enters into the body of the 

 Beroes, and the rapid circulation of water which is appar- 

 ent throughout their frame, we would naturally suppose 

 that any tinge which the body might accidentally acquire 

 would be extremely fugitive. It was found, however, to 

 be much less so than d priori would have been expected. 

 My attention was drawn to this peculiarity by the circum- 

 stance of all my glass vessels being one evening occupied 

 by Beroes and Crustacea, so as to compel me to place a 

 small Medusa in a tin vessel, which chanced to be rusted 

 at the seams. Next morning the colorless appearance of 

 the animal was changed into a bright yellow, which ap- 

 peared to pervade every part, and doubtless arose from 

 the oxide of iron diffused through the sea- water. This 

 tint remained during the entire day, although the animal 

 was transferred to pure sea-water. Wishing to try if the 

 vessels of the Beroe would become distinct, if filled with 

 some colored fluid from which the animal could suddenly 

 be withdrawn, and viewed through the usual transparent 

 medium of sea-water, I placed a Beroe in a weak infusion 

 of saffron. At the end of twenty minutes its color had 

 undergone a perceptible change. I allowed it, however, 

 to remain immersed for about six or seven hours, when 

 it had assumed a bright yellow hue. It was then placed 

 in pure sea-water, but retained its yellow color for twenty- 

 four hours afterward; and though it gradually became 

 fainter, it was very perceptible even at the expiration of 

 forty-eight hours." 



