44 



fenestrated. The ventral transverse rods join with their points but do 

 not cross one another - - at least not in this stage. 



It should be pointed out thai the figure of this larva is drawn from 

 a preserved specimen, so that it is very probable that there is some shrink- 

 age in the soft parts of both body and arms. 



Toxopneustes roseus (A. Ag.). 



PI. VIII. Fig. 7. 



Fertilization of this species was undertaken on November llth at 

 Taboga, Panama. It was, evidently, at the end of its breeding season, 

 most of the specimens being empty. 



The eggs are of the usual small size, transparent, though somewhat 

 yellowish. The cleavage does not present any unusual features. At the 

 age of 24 hours the embryos show the first rudiments of the skeleton; 

 at the age of two days they have the typical pluteus shape of the first 

 stage. The body skeleton forms a basket structure, the postoral rods 

 are fenestrated. - - On the following day the larvae all died, and there was 

 no possibility of getting a new culture. Xo figures were drawn of the 

 young larvae; since the skeleton has been dissolved in the preserved 

 specimens, there is no reason to give any figure to show the general shape 

 of the larva, which is as usual. 



Although I did thus not succeed in rearing this larva beyond the first 

 stage, I think I can give some information also of the somewhat more 

 advanced stage. In a plankton sample from November 1915 from near 

 Taboga was found the larva represented in PI. VIII Fig. 7. It is almost 

 beyond doubt that it must be the larva of Toxopneusles roseus. The regular 

 Echinoids occurring at Taboga are the following: Eucidaris Thouarsi, 

 Diadema rne.ricanurn, Astropyga pulvinata, To.iopneustes roseus, Lytechi- 

 nus panamensis and Echinometra van Bnmti. Diadema was not ripe at 

 that time and is therefore out of question; the young stages of Eucidaris 

 described above are so different from this larva that it is hardly imagin- 

 able, how it could develop into a larva like the one in question. The Aslro- 

 pyya- and Lytechinus-larva. are quite different (see PL V Figs. 6 7 and 

 PI. VII Fig. 4); also Echinomelra van Bnmti was reared to the young 

 Pluteus, the body skeleton of which forms a strongly thorny basket 

 structure. Thus Toxopneustes roseus alone remains to which to refer 

 this larva. 



Characteristic of this larva is the considerable length of the ventral 

 transverse rods, which are crossing one another and make the median 

 part of the postoral band project as a pair of small lobes, supported 



