no 



species il belonged. Fortunately, II. Lyman Clark, who was a member 

 of the Carnegie Expedition to Torres Strait, 1913, — on which Dr. D. H. 

 Tennenl reared the larvae (at Badu Island), which made the object of 

 Miss Medes' paper — was able to inform me I ha I the species in question 

 was Peronella Lcsueuri: he. moreover, sent me a specimen lioiu Hadu 

 Island, thus enabling me to compare it directly with my .Japanese spec- 

 imens and lo convince myself of their identity.') 



The material studied by Miss Medes represented only two stages, of 

 29 and 55 hours respectively. The latter was used only for the study of 

 the skeleton, especially the development of the spines being very carefully 

 worked out. There was thus only the stage of 29 hours left for the study 

 of the larval structure, and accordingly the results could only be very 

 incomplete. The fuller report of the development of this species given here 

 is thus by no means made superlluous by the said paper, the less so as 

 the interpretations given in that paper are not all of them acceptable. 



The material lor the study of the (leveloj)ment of this species, which 1 

 collected in .Japan, is rather rich and well ])res(Tve(l and allows giving a 

 fairly complete record of at least the younger stages. It has been possible 

 to establish beyond doubt most of the remarkable facts revealed by the 

 study of this form, so strongly deviating from the usual type of develop- 

 ment in Echinoids, although less deviating than the other Echinoid with 

 shortened development studied in the present work, Heliocidaris erylhro- 

 f/ramma. The later stages of metamorphosis as well as the (leveloi)ment 

 of the adult skeleton and the postlarval development upon the whole have 

 been rather disregarded, such monographic study being out of the plan 

 of the present work. 



The adult Peronella Lesueuri was found in considerable numbers in the 

 sandy bottom of a shallow lagoon close to the Biological Station at Misaki ; 

 they were found lying buried in the sand, only a few centimeters down, 

 a small elevation indicating their place. They were found to have ripe 

 sexual products in the latter part of .June and in .July. Fertilization was 

 undertaken on June 19th and repeatedly during the following three weeks. 

 Metamorphosis was completed in the cour.se of 3 — 4 days. The meta- 

 morphosed urchins very soon died, assuming the green colour so character- 

 istic of dead Clypeastroid tissue. Wishing, if possible, to keep the young 

 urchins alive and to follow their further growth changes 1 tried to keep 

 them in dishes with a more natural bottom consisting of sand taken from 



•) The specimen from Badu dilTers slightly in shape Iroiii the .lapanese specimens. The 

 species being known lo he highly variable in regard to the oiilline of the test, the dilTerencc 

 is not at all surprising. Perhaps, however, a closer study of the (lilTerenl forms, both in regard 

 to their general characters and their development, niay ultimately prove that what we now 

 regard as one very variable species really is a group of closely allied but distinct species. 



