62 



posterior transverse rod especially indicating thai it can hardly be so 

 very closely related to those forms. 



Evechinus chloroticus (\ 7 al.). 



PI. X, Figs. 15. 



During a trip round the North Island of New Zealand, onboard the N. 

 Z. (1. S. "Hinemoa" I had the opportunity of rearing the larva of this 

 species. Fertilization was undertaken on the 18th of December 191-1. The 

 culture of the larva* was kept until the 22nd of January 1915; the larvae 

 had attained their full size by that time, but metamorphosis had not 

 yet begun. The development of this species then goes on rather slowly, 

 though perhaps not quite so slowly in nature. The conditions under 

 which the cultures had to be kept onboard the small steamer were not 

 the very best, and this may perhaps have had some delaying influence on 

 the development, as also the fact that not few of the larvae showed more 

 or less pronounced abnormalities most probably is due to some extent to 

 these conditions. The fact that the two cultures which were made showed a 

 rather marked difference in the time of appearance of the skeleton indicates 

 that this supposition is correct. But, anyhow, a good number of the larvae 

 developed normally, and a fairly complete description of the larva of this 

 species thus can be given. - Unfortunately there was no possibility of 

 making drawings from the living specimens, and moreover it happened 

 that in all the specimens of the more advanced larvae preserved the skeleton 

 had been dissolved (while the shape was preserved quite exceptionally 

 well); only in some larva 1 of the first stage the skeleton remained intact 

 but all of them present some abnormalities. The description of the 

 skeleton thus cannot be quite satisfactory; but the main features at least 

 can be ascertained from this material combined with the notes put down 

 after observations, on the living specimens. 



The cleavage is quite regular; the 8-cell stage was reached in the course 

 of 4 hours; swimming blastulae were found ca. 16 hours after fertilization, 

 and the gastrula stage was reached at the age of about 24 hours. They 

 were not very clear and evidently do not form a very good object for mi- 

 croscopical study. The skeleton had appeared on the 3rd day and the em- 

 bryos were beginning to assume the Pluteus-shape. In another culture 

 the skeleton began to form in the course of the second day. At the age 

 of 6 days the larva? were found to be well developed Plutei in the first 

 stage; in this stage they remained apparently unaltered for about 8 days 

 more; at the age of nearly two weeks the first indication of the postero- 

 dorsal arms appeared. At the age of three weeks the stage shown in 

 PL X, Fig. 2 was reached, and the fully formed larva shown in PI. X, Fig. 3 



