302 TADPOLES OF THE SEA 



or marked with only a rare patch of red or violet colour. 

 They are not often seen in the stormy, muddy seas of the 

 English coast, but occur far out at sea and in the Medi- 

 terranean. In the quiet sea-lochs of Scotland and in the 

 Norwegian fiords they can be captured with the towing- 

 net a wide-mouthed bag of bolting cloth attached to a 

 rope and towed by the naturalist behind his boat. I made 

 my acquaintance with this peculiar world of life many 

 years ago in the Mediterranean. It includes glass-like 

 fishes (the young stage of eels), crystalline shrimps, worms, 

 jellyfish (medusae), swimming snails, and a vast number of 

 minute transparent larvae, or young forms of animals, 

 which in later life sink to the bottom. But the most 

 curious and characteristic members of this special glass- 

 like floating population are certain transparent Ascidians 

 called salps or Salpae, which are very abundant in the Bay 

 of Naples and in the warmer seas. A few years ago I 

 met one species of them in great numbers when I was 

 swimming in the sea near Dinard, on the Brittany coast. 

 Big salps an inch to three inches long transparent oblong 

 sacs, widely open at each end are commonly found in 

 the Bay of Naples, slowly swimming by a very gentle 

 contraction and expansion of the walls of the sac. They 

 are Ascidians, like in general build to the constituent 

 individuals of the sea-candle colonies, but much bigger. 

 Big specimens of Salps are as much as three inches in 

 length. The salp is like a transparent, oblong packing- 

 case, with the small ends knocked out. The wide opening 

 at one end is the mouth, that at the other is the gaping 

 orifice of the peri-branchial chamber. The whole salp 

 seems little more at first sight than a huge gullet, which 

 opens at one end by the mouth, and by large slits in its 

 sides is continued into the equally large branchial 

 chamber, which gapes widely at the other end of it. You 

 can put a pencil through the animal into one end and 



