^V' 



Fig. 26. Echinodcrin larvae etc. 



1 . Bipinnaria larva of a starfish, Astcritis glcKialis. 



2. Brachiolaria larva of .4.s7(Ti<7^- ruheus. 



3. Auricularia larva of a sea cucumber, Synapta digitata. 



4. Doliolaria larva, or pupa, of Synapta. 



5. Plutcus larva of Brittle star, Ophiura texturata. 



6. Pluteus larva of Brittle star, Ophiothrix J'ragilis. 



7. Plutcus larva of sea urchin, Eiliiiiocardiuiu cordatuin. 



8. Tornaria larva of the acorn-worm, Balaiwglossus (a Hemichordate). 



The first four are to the same scale. 



Shetland and in Norwegian waters between 60° and 62° N. Berried females 

 have never been found north of 57'' N west of Scotland and only rarely north 

 of about 54' N, whereas phyllosomas have been found frequently off the 

 north-west of Scotland and even as far afield as Faroe. 



The ordinary lobster has an ordinary and typical decapod life history and 

 a young one from the plankton is shown in Plate XXV. 



The Echinodcrniata — starfishes and sea urchins and sea cucumbers — have 

 planktonic larvae, some of them of exotic shape (Fig. 26). The ordinary 

 asteroid starhsh (like the common starfish) have a larva called a bipinnaria, 

 which is not unlike the 'auricularia' larva of the sea cucumber. This gradually 

 changes to a 'brachiolaria' which metamorphoses into a tiny starfish (Plate 

 XXVI). The larvae of the brittle stars and sea urchins are also similar to each 



90 



