12 



me to join the "Hinemoa" on its trip round the North Island of New 

 Zealand, and to the Director of the Carnegie Institute for allowing 

 me to include in this report the results obtained during the Expedition to 

 Tobago B. W. I. — For the hospitality offered me from the Phihppine, 

 the Japanese and the Austrahan Government I shall have to thank at 

 another occasion, having to confine myself at present to what has a con- 

 nection with the present work. 



It may be practical, and useful, to give here a short summary of what 

 has been accomphshed hitherto in the study of the larval forms of the 

 different species of Echinoderms, either by direct rearing of the larvae or 

 by identifying the pelagic larvae found in the plankton, tracing their 

 origin through combinations of known facts. 



From this summary are omitted all larvae not traced with any reason- 

 able degree of certainty to their parental forms. Further viviparous 

 forms or such as protect their young, the embryos not having a free or 

 pelagic stage, are not mentioned. Likewise such cases, where only the 

 postembryonal stages are described (e. g. several species of Comatulids), 

 are omitted from this summary. Observations relating only to the fertiliza- 

 tion, cleavage and gastrulation, but not carried so far as to the beginning 

 larval form are generally not considered either; further generally no men- 

 tion is made of the great number of papers relating to experimental 

 studies on the larvae — treatment with various chemical agents, hybridiza- 

 tion etc. — , except in cases where also pure bred larvae are reared. 



The enumeration of the species mentioned follows the systematic ar- 

 rangement, not the chronological order of the observations. The arrange- 

 ment is that adopted in the special part of this work, beginning with the 

 Echinoidea. 



I. Echinoidea. 



Cidaris cidaris (L.) (Syn. Dorocidaris papillata); reared until nearly the 



full larval shape by Prouho, 1888. 

 Arbacia lixula (L.) (Syn. Arbacia pustulosa Gray; Echinocidaris eequi- 



tuberculata (Blv.)); reared by W. Busch, A. Krohn, 1853, 1854, 



to first larval stage; the fully formed, pelagic larva identified by 



Joh. Mil Her, 1853; reared through metamorphosis byGiesbrecht 



1909 (in V. Ubisch, 1913). 

 Arbacia pundulata Gray; reared to full larval shape by Fewkes, 1880; 



to full larval shape by Brooks, 1882, through metamorphosis by 



Garman & Colton, 1882. 

 Psammechiims miliaris (Mull.) (Syn. Echinus, Parechinus miliaris); pelagic 



