THE LAEVA OF ASTERIAS VULGAUIS. 105 



The Larva of Asterias vulgaris. 



By 



Ocorg;e W. Field, M.A. 



With Plates XIII, XIV, and XV. 



This work was undertaken at the suggestion of Professor 

 W. K. Brooks for the purpose of getting, if possible, some 

 further hint upon the significance of the larval form in Echi- 

 noderm phylogeny. It was carried on from October, 1889, to 

 April, 1891 ; from June to October, 1890, at the Laboratory 

 of the United States Fish Commission at Wood's Hall, Massa- 

 chusetts, where the living auimals were studied, and for the 

 remainder of the time in the Biological Laboratoi-y of the 

 Johns Hopkins University, where the work was upon the pre- 

 served material. My heartiest acknowledgments are due to 

 Professor Marshall McDonald, U.S. Fish Commissioner, for the 

 advantages furnished at the Grovernment Laboratory ; and to 

 Professor Brooks, of this university, who has so kindly placed 

 at my service the preserved material, the preparations, and 

 drawings, which formed the basis of his recent paper before 

 the National Academy (4) . 



The material was obtained by means of the surface net, and 

 was supplemented by that obtained by artificial fertilisation. 

 The larvae reared by the latter process were kept in glass 

 beakers containing fronds of Ulvacese, which served both for 

 aeration and by the liberation of zoospores furnished to some 

 extent food for the developing larvae. The larvae were daily 

 transferred with a pipette to beakers of fresh sea water. The 



