JELLY-FISH 



323 



The Thaumantia is an exceedingly common form, with a four-section bell- 

 shaped disc. 



Tunis digitalis is a brightly coloured, cone-shaped species, very much 

 smaller in size. 



The Tube-mouthed Sarsia (Sarsia tubulosa) is a very small species, about 

 \ inch in height, with a stomach like a bell-clapper, twice as long. 



Off the Devon and Cornish coasts there is frequently found a very beau- 

 tiful glass-like species, tinted blue, and with curved lines of crimson, known 

 as Mquorea forbesiana, about 4 inches across. 



The Sea Acorn, SEA GOOSEBERRY, or BEROE (Pleurobrachia pileus) is 

 quite common, yet seldom seen, being almost transparent and very small. 



not. 



7KUK 



A, side view of Ascidian larva; B, side view of adult Ascidian 

 cut open; a (in A), position of future anus; (in B), anus; br 

 (in A), hollow brain vesicle ; (in B), ganglion remnant of larval 

 brain; fix, pagillae by which the larva attaches itself; g (in A), 

 single gill-pore on one side ; (in B), trellis- work on side of the 

 adult gullet which develops out of the gill-pore of larva ; muse., 

 dotted lines indicating outlines of muscle cells which flank the 

 tail on either side; nerv., spinal cord of larva; not., notochord 

 or rudimentary backbone of larva. 



Round its oval body are eight narrow bands, on which are the many " paddles " 

 by which it moves itself through the water, giving remarkable flashes of coloured 

 light, with prismatic effects. 



At this point, although entirely out of place, mention may be made of 

 some other curious marine creatures, one of which at least is not infrequently 

 mistaken for some sort of jelly-fish. I refer to the Ascidians or Tunicates. 



These are really a class of " survivals of ancestral vertebrates " that have 

 degenerated in the course of time. When young they are active swimmers, 

 have a brain, a spinal cord, and a rudimentary backbone; but they attach 

 themselves to rocks, and soon lose these parts, becoming no more than living 

 " filters " for the rest of their existence. Some are known as Sea Squirts, 

 and are pear-shaped, jelly-like masses, quite firm to the touch, planted firmly 



