64 SQUIRTS, POLYPS, AND JELLY-FISHES. 
after them ; others, again, are darting actively along, 
propelled by successive pulsations of their trans- 
parent bells. It is at first difficult to conceive that 
these delicate films are indeed masses of organized 
animal matter, so frail and evanescent do they ap- 
pear as they noiselessly slip by. But scoop up a 
Clytia, or a Dactylometra (Pl. 4, Fig. 6), and ex- 
amine the animal leisurely in the jar that has been 
brought for that purpose. Structures that escaped 
our attention before are now distinctly visible. The 
pulsating bell is the first object to attract our no- 
tice. Its perfect transparency permits us to see, 
suspended from the centre of the interior, a pe- 
culiar pouch-like body, at the extremity of which 
is situated the mouth. The water entering by the 
mouth passes into the hollow of the pouch or manu- 
brium, whence it is in great part distributed to the 
four radiating canals which descend the sides of the 
bell to its base and divide it into four equal parts. 
These vessels, which constitute a part of the circu- 
latory system of the animal, merge into a common 
marginal ring which surrounds the base of the bell. 
From this ring are given off a number of long pro- 
cesses, known as tentacles, each of which is pro- 
vided with the very remarkable stinging nettle- or 
lasso-cells to which reference has been made in our 
description of Pennaria. 
This, then, is the substance of our medusa—a 
quantity of water encased in a thin film of animal 
matter. Place your finger gently on the bell, and you 
will probably be unable to detect its presence there. 
Take the animal from the water and expose it to 
