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species it belonged. Fortunately, H. Lyman Clark, who was a member 

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

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

 Miss Medes* paper — was able to inform me that the species in question 

 was Peronella Lesueuri; he, moreover, sent me a specimen from Badu 

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

 imens and to convince myself of their identity, i) 



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 superfluous by the said paper, the less so as 

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



The material for the study of the development of this species, which I 

 collected in Japan, is rather rich and well preserved 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 erythro- 

 gramma. The later stages of metamorphosis as well as the development 

 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 course 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 I tried to keep 

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



1) The specimen from Badu differs sliglitly in sliape from tlie Japanese specimens. Tlie 

 species being known to be liiglily variable in regard to tlie outline of the test, the difference 

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

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

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



