74. THE HAUNTS OF LIFE 
one must not forget the family of Open-Sea 
Insects. 
Molluscs are represented by the Sea-Butter- 
flies and other lightly built translucent Gas- 
teropods, and by a number of active cuttle- 
fishes, such as the Argonaut and some squids. 
Just across the border-line separating the 
backboned from the backboneless animals is 
the class of sea-squirts or Tunicates, and it is 
interesting to find a few of these in the Open 
Sea which do not degenerate as their shore- 
relatives do, but keep up the promise of their 
youth. Others form free-swimming colonies 
like the brilliantly luminescent Fire-Flame, 
sometimes as long as one’s arm, and with a 
light that one can read a few words by. Highly 
fitted for open-sea life are the Salps, some- 
times like single barrels of glass, two or three 
inches long, sometimes in long chains, which 
swim gently like glass-serpents in the sea. 
The rest of the roll is easy,—the open-sea 
fishes like the flying gurnard, some turtles and 
sea-snakes, some birds like petrels and penguins, 
and then the whales among Mammals. It is evi- 
dent that the Open Sea has its share of variety. 
