92 



found in the regular Echini at once excludes both the Spatangoids, the 

 Clypeastroids and the Cidarids, the two former having quite another 

 type of ophicephalous pedicellariae, the latter being entirely devoid of that 

 type of pedicellarise. Reviewing the regular Echini, other than Cid- 

 arids, occurring in the West Indies, it seemed evident that Echinometra 

 lucunter was the only form that could come into consideration, taking 

 for granted that only littoral forms could come into regard when seeking 

 for the parental origin of these larvse, which were found to occur in fairly 

 good numbers in the littoral waters. The premises were apparently quite 

 correct. Nevertheless the conclusion was wrong. It is not the larva of 

 Echinometra lucunter; that larva, reared from the egg through metamor- 

 phosis, as described and figured in the present work (p. 71 ; PI. I, Figs. 

 1 — 2) has quite the typical shape of Echinoid larvse. — There was at that 

 time also some uncertainty regarding the larva of Diadema antillarum, 

 it being only from inference concluded that the Diadema-larvsL would be 

 found to resemble the Echinopluteus Mijlleri, viz. that larva from the 

 Mediterranean which has been, though without sufficient evidence, 

 referred to Centrostephanus longispinus, a near relative of Diadema. Al- 

 though the development of Diadema is still only incompletely known, the 

 shape of the young larva, reared by the present author (see above, p. 25 

 Pl.V, Fig. 5) gives sufficient evidence that it has nothing 

 with the Echinopluteus transversus to do, and Diadema is 

 then also really out of question as the parent of this larva. 

 There must therefore be something wrong in the premises, 

 either so that the type of ophicephalous pedicellarise found 

 in the larva may be found also in other forms than the 

 regular Echini, save the Cidarids, or that the larvse may 

 Fig. 37. ophice- belong to deep-sea forms. Regarding the latter eventuality 

 phaious pedicel- I would say that — although it can scarcely be doubted 



lana of Echino- ., ^ , t^ , . . , 



piuteus transver- ^^y ^^^^ ^hat some deep-sea Echinoids have true pelagic 

 sus, species e. larvse — the fact that two species of this larval type were 

 "'"/i- found near the island of Taboga in the inner part of the 



Gulf of Panama, very far from the deep sea, decidedly speaks against the 

 suggestion that the larvse might belong to deep-sea forms. 



The ophicephalous pedicellarise (Fig. 37) are decidedly of the type 

 known to occur only in the regular Echinoids. Of these Arbacia, Diadema, 

 Tripneustes, Lytechinus and Echinometra are all excluded, their larvse 

 being known more or less completely. The fact that there are two species 

 of larvse from the Gulf of Panama very closely related to two other species 

 from the Westindies would seem to preclude the idea of taking forms like 

 Salenia, Coelopleurus, Podocidaris, or any of the Echinothurids or the 



