viii CONTENTS 



Strongylocentrotus, Sphaerechinus, Echinus and 



Echinocardium 26 



Asterias 26 



Asterias forhesii and A. vulgaris 26 



Asterias glacialis 28 



Thy one 29 



Synapta 29 



Nereis limhata 29 



Platynereis dumerilii 31 



Chaetoptertis 32 



Podarke 32 



Amphitrite 32 



Phascolosoma gouldii 33 



Phascolosoma vulgare and Ph. elongatum . ■■ • 33 



Cumingia 33 



Ensis 33 



Mytilus 34 



Mya 34 



Mactra 34 



Pecten 35 



Crepidula 35 



Aplysia 35 



Loligo . '. 36 



Cynthia, Molgula, Ciona 36 



Phallusia 37 



Amphioxiis 37 



Fundulus 37 



Literature 38 



IV. Some Methods for Preliminary Experimental 



Manipulations 41 



Methods for removing the jelly from the eggs of 



echinids 41 



Methods for removing the vitelline membrane from 



inseminated echinid eggs 43 



Methods for inducing membrane-separation in 



unfertilized echinid eggs 44 



Methods for inducing membrane-separation in 



unfertilized eggs of the genus Asterias 47 



