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ECHINODERM LARVJE. 495 



Plate I. 



Figs. 1 to 9. Stages of development of Asterias rubens. 

 Optical section of blastula. 

 Optical section of early gastrula. 

 Optical section of later gastrula. 

 Ventral view of an early bipinnaria. 

 Slightly diagrammatic optical section of 



bipinnaria of about tbe same age. 

 Ventral view of an older bipinnaria. 

 View from tlie left side of a bipinnaria of about 



the same, age. 

 Ventral view of a fully-formed bipinnaria. 

 Dorsal view of a still older bipinnaria. 

 Ventral view of bipinnaria of Asterias glacialis. 



(Compare with fig. 9). 



Plate II. 



Fig. 11. Bipinnaria of Luidia ciliaris, viewed from the 



left side. 

 Fig. 12. Ventral view of a slightly older bipinnaria of 



same. 

 Fig. 13. Brachiolaria of an Asterid not yet identified, 

 undergoing metamorphosis. Viewed from 

 the left side. 

 Figs. 14 to 18. Stages of the development of Solaster 

 endeca (?). 

 Young larva, viewed from the right side. 

 Older larva, viewed from the left side. 

 Still older larva, in which the larval arms are 



fully developed. 

 Oral view of a larva towards the end of the free- 

 swimming stage. 

 Larva of (?) Solaster sp., viewed from the righl 

 side. 



Fig. 



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