300 TADPOLES OF THE SEA 



when touched or otherwise excited, these " sea candles " 

 glow all over with a strong yellowish light. They are not 

 fixed, but float together in great shoals in the sea, and 

 when a boat runs into such a floating crowd of these 

 curious marine " candles " the waters " blaze " over a large 

 space with their brilliant phosphorescence. The cylinders 

 of Pyrosoma consist of clear, tough jelly — they are hollow 

 and open at each end — and the jelly is raised into glass- 

 like pointed projections all over the surface. This tough 

 crystal-like jelly is the common coat or tunic of an 

 immense number of little Ascidians which have produced 

 it as they budded and multiplied from an original single 

 little Ascidian. They are all set in the jelly, so that 

 each has its mouth opening on to the outer surfacfe 

 of the cylinder, whilst the aperture of the peri-branchial 

 chamber is at the other end of the little animal and 

 opens into the long axial cavity of the cylinder. A well; 

 grown cylinder is built up by some hundreds of indi- 

 vidual Ascidians, and a slice across its length shows from 

 eight to a dozen of them set radially in the ring of 

 jelly, cut off like a slice of a hollow cucumber. The little 

 Ascidians are each about a third of an inch in length, cor- 

 responding to the thickness of the jelly-wall in which they 

 are set. They are all in connection with one another by 

 strands of living tissue. They continually bud, and also 

 form new jelly — thus adding to the size of the colony, 

 new individuals being budded so as to occupy positions 

 between the older ones. The whole colony increases in 

 bulk by " interstitial growth." They also produce, from 

 time to time, each a single egg, which is fertilised within 

 the parent, and grows into a little chain of four minute 

 Ascidians surrounding a larger central one, before it is 

 set free, and floats out of the central chamber of the 

 " colonial cylinder " to start a new floating colony. 



Each of the transparent little Ascidians of a Pyrosoma 



