278 



TADPOLES OF THE SEA 



The Neapolitan fishermen, unlike their northern brethren, 

 have names for several kinds of Ascidians and for a great 

 number of the marine creatures of no market value, 

 which they come across in searching the shallow regions 

 of the Bay of Naples for shell-fish. 



If you cut one of these Ascidians open with a pen-knife 

 you will find that the sac is very thick and tough, though 

 translucent. Within it you will see a coiled intestine, 

 surrounded by reddish-coloured soft material. Careful 



FIG. 32. A dissection of an Ascidia. The thick-walled sac has been 

 cut all round and half of it removed. We see on the left (at the top) 

 the mouth leading into the enlarged gullet, perforated like trellis- 

 work, and from this we trace the re-curved intestine which opens 

 into the peri-branchial chamber on the right. This chamber itself 

 opens to the exterior by the spout-like process on the right. Lying 

 in the chamber just above the anus is a single egg. Above the egg 

 we see a pale oblong body, pointed at each end. This is the brain. 

 In the "body-cavity " around the intestine many eggs are seen, and 

 at the lower end of it a curved striped body which is the heart. 



dissection of the dead Ascidian with the aid of a lens and 

 delicate forceps and scissors, when it has been pinned to 

 a leaded plate of cork in a shallow dish containing weak 



