128 



is a very faint indication of yellow color at the point of these arms. The 

 stomach has assumed a faint yellowish tint. The red pigment at the base 

 of the posterolateral arms is indicated already in the stage represented in 

 PL XX, Fig. 1. 



Beyond this stage I did not succeed in rearing this larva, the culture 

 being only small. Still the result acquired is sufficient for showing the very 

 close resemblance of this larva with that of Ophiothrix fragilis. Only in 

 the pigmentation there appears to be a distinct difference between these 

 two larva, that of the 0. fragilis-larysL being black. Also the time required 

 for the development appears to be rather different in the two species; at 

 least the earlier stages require much shorter time in angulata than in fragilis. 

 It would appear to be characteristic of this larval type (and perhaps 

 of all larvae of Ophiothrichidse) that the oral lobe is late developing, the 

 ciliated bands going in a nearly straight line along the anterior border 

 of the body, whereas in other Ophiuroid larvae the oral lobe develops much 



earlier. (This characteristic 

 young stage of the Ophio- 

 thrix larva was figured al- 

 ready by Job. Miiller in his 

 V. Abhandl. Taf. VI. Fig. 8). 



Species b. (Pl.XIX,Figs. 

 3 — 6). This larva is charac- 

 terized by the great length 

 of the posterolateral arms, 

 which are generally about 

 6 — 7 times the length of the 

 inner arms; these arms also 

 form a more obtuse angle 

 than in species a, in fact, 

 they may almost make a straight line. Otherwise there is no noteworthy 

 difference from species a. Also the skeleton (Fig. 54) is alike, only the 

 body rods being slightly shorter. The pigmentation appears to be as in 

 species a, black spots on the posterolateral arms. 



As seen by a comparison of the figures quoted, there is a rather consider- 

 able amount of variation among the larvae referred to this "species", both 

 with regard to the length and the outward direction of the posterolateral 

 arms. Possibly they represent in reaUty two different species. The spec- 

 imens figured are all from the Gulf of Panama. Now, so far as I can see, 

 without going too deep into Utterature, only one species of Ophiothrix, 

 0. spiculata Le Conte, has been recorded from there; but it can hardly 



Fig. 54. Skeleton of Ophiopluteus of Ophiothrix, 

 species b. "w/i- 



