SEA-UKcnms and sea-cucumbeks. 34c 



while yet the beauty and freshness of life remain. 

 And moreover, with care and prudence, some selected 

 subjects may be maintained in vigour, at least long 

 enough to aftbrd you valuable information on the 

 liabits, economy, metamorphosis, and development of 

 animals, of which even the scientific world know^s 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 tlie microscope. It is just visible to the un- 

 assisted 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 dis- 

 tinctly made out in all its parts, and is an object of sin- 

 gular elegance and beauty. 



It is, as you see, somewhat of the figure of a hel- 

 met ; the crest rising to a perpendicular point, which is 

 rounded, the vizor 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 the first thing that strikes us is, that a frame-work 

 or skeleton of extreme delicacy, composed of glassy 

 rods, supports the whole structure. Look carefully at 

 this, and mark its symmetry and elegance. Tliere is, 

 then, first, a rod which passes through the crest per- 

 pendicularly, and carries at its lower extremity a hori- 

 zontal ring. To the opposite sides of this ring are 

 15* 



