71 

 Echinometra lucunter (Linn.) 



I'l. 1, Fifjs. 1 -2; I'l. XU, Fig. 1. 



During my visit lo Tobago H. \V. I. wilh Ihe Carnegie Expedition in 

 1916 I had the opportunity of rearing this species. FertiUzation was under- 

 taken on [he 2 nil of March and again on the 2ncl of April; by this time 

 the breeding season was in the main over, only some few small specimens 

 still having ripe sexual products. Both cultures were perfectly successful, 

 metamorphosed young being obtained from both. Un leaving Tobago 1 

 carried some of these onboard the steamer to New York; during the 

 lime from the 9th to tlu' ISth of May they were kept in the New York 

 Aquarium and thereafter again carried onboard the steamer to Copen- 

 hagen. At the arrival there, on June 1st, two specimens were still aUve, 

 although they had hardly grown, which is naturally explained by the 

 fact that it was impossible to procure a good food supply lor Ihem; it 

 was also impossible lo secure a constant, congenial temperature. That 

 it was possible to carry them so far, in spite of these adverse conditions, 

 is of considerable interest and plainly indicates that much more may be 

 done in this way. 



The eggs are small, ca. 0.12 mm, opaque, and the embryos are like- 

 wise very opaque and no good objects for microscopical study. I have 

 omitted to note the time it takes to pass the difl'erenl developmental 

 processes, but the lirsl j)luteus stage is reached on the second day. At 

 the age of 4 days the postero-dorsal arms began to appear, and in the 7 

 days old larvae (PI. XII, Fig. 1) I found the absorption of the body skeleton 

 in progress. The posterior transverse rod appeared on the 10th day and 

 metamorphosis was completed or nearly so at the age of 19 days. 



In Ihe first Pluteus stage the larval body is short, obliquely truncated. 

 The young larva is rather strongly pigmented by red pigment cells and 

 not very transparent. In specimens 6 — 7 days old a distinct nerve band 

 was noticed across the corners of the anal lobe (PI. XII, Fig. 1). .Mthough 

 this structure cannot be observed in the preserved specimens, I would 

 venture to see herein an indication that this larva (and probably inany 

 others) has a nervous system similar to that of the larva of Echinociiamus 

 pusilliis as recently described by mc^). 



The skeleton (Figs. 25 A — B) forms a complicated basket structure; 

 the recurrent rod is double, two large meshes being thus formed on each 

 side of the body, sometimes also some smaller additional meshes at the 

 lower end, on account of secondary ramifications. The body rod is strongly 

 thorny. The postoral rods are fenestrated, rather strongly thorny. — Judg- 



') Notes on the dcvelopmenl and llic larval forms of some Scandinavian Echinoderms. 

 Vid. Medd. Dansk Naturli. l-orcn. 71. Iil2(t. p. 137. 



