THE DEVilLOPMENT OF ECHINOIDS. 335 



The Development of Echinoids. 



Part I. — The Larvae of Echinus miliaris and Echinus 

 esculentus. 



By 



E. IV. MacBride, M.A., 



Professor of Zoology in McGill University, Montreal. 



With Plate 33. 



The development of Echinoids is up till the present very 

 imperfectly known^ our information on the subject being in a 

 most unsatisfactory condition. The foundation was laid by 

 Johannes Miiller (3), but although he observed and described 

 the external features of the metamorphoses, he was unable to 

 refer with any certainty any one of the larval forms which he 

 described to the adult species from which it was derived. So 

 far as I am aware. Prof. Theel (4) and H. Bury (1) are the only 

 persons who have hitherto reared any species from the egg until 

 the conclusion of the metamorphosis. Through the researches 

 of the former we have obtained an accurate knowledge of the 

 characters of the larva of Echinocyamus pusillus at all 

 stages of its growth. The youngest larval forms of many species 

 have been determined by rearing, nevertheless Mortensen (2), 

 in his most valuable summary of all descriptions yet pub- 

 lished of Echinoid larvae, points out that our knowledge of the 

 later pluteus stages is most imperfect, and that it is not possible 

 to assign the older plutei which have been described to the 

 species from which they have been derived. 



