340 EVENINGS AT THE MICROSCOPE 



off into the receiver. After a few such essays, unless you 

 have very bad success indeed, you will see even with the 

 naked eye, but much more with a lens, that the water in 

 your jar is teeming with microscopic life; and though 

 many of your captives will not long survive the loss of 

 their freedom, still meanwhile you may secure many an 

 interesting object, and examine it, while yet the beauty 

 and freshness of life remain. And moreover, with care 

 and prudence, some selected subjects may be maintained 

 in vigor, at least long enough to afford you valuable in- 

 formation on the habits, economy, metamorphosis, and 

 development of animals of which even the scientific world 

 knows next to nothing. 



I have just been so fortunate as to obtain in this way 

 the larval stage of one of our Sea-urchins, and have it 

 now in the thin glass trough which is on the stage of the 

 microscope. It is just visible to the unassisted sight as 

 a slowly moving point in the clear water, when the 

 vessel is held up to the light; but with the low power 

 which I am now using, it is distinctly made out in 

 all its parts, and is an object of singular elegance and 

 beauty. 



It is, as you see, somewhat of the figure of a helmet; 

 the crest rising to a perpendicular point, which is rounded, 

 the visor or mask descending far down and ending in two 

 points, and a long ear hanging down on each side, so as 

 to reach the shoulders of the wearer. Of course such 

 comparisons are fanciful, but they assist one in intelligible 

 description. 



Now, the entire helmet is composed of a gelatinous 

 flesh of the most perfect transparency, so that we can see 

 with absolute clearness everything that is within it. And 



