57 



are seen to consist of two parallel, closely apposed parts, which fact most 

 probably indicates their origin as a fold of the ciUated band. The process 

 of their formation was not observed on the living material. There is a 

 pair of small, earshaped posterolateral processes, supported by branches 

 from the posterior transverse rod. No antero-dorsal arms are developed, 

 and there are no processes from the dorsal arch to support lobes of the 

 dorsal vibratile band. The antero-lateral and preoral arms are rather 

 short and narrow. The preoral band is almost straight, the postoral band 

 slightly concave in the middle, bending rather abruptly downwards at 

 the sides, whence it passes into the band of the postoral arms. There 

 are no vibratile lobes. Pigmentation is inconspicuous; there are no large 

 pigment spots in the point of the arms, only scattered pigment cells in the 

 body and along the arm rods. 



In the body skeleton absorption has begun in this stage (Fig. 19) and 

 a posterior transverse rod has been formed. This is very characteristic; 

 it is a Uttle curved and ends in two branches, one simple, slightly curved, 

 upwards directed, the other larger, obliquely downwards directed; this 

 latter branch bifurcates, the divisions again branching somewhat irregular- 

 ly. It is this branch which supports the postero-lateral process. Both 

 the postoral and the posterodorsal rods are fenestrated and rather strongly 

 thorny; the simple rods supporting the anterior arms are finely thorny, 

 judging from the young larva preserved; the skeleton has been dissolved 

 in the preserved specimens of the fully formed larva, and it was omitted 

 to make notes or figures thereof from the living specimens. — Pedicella- 

 rise have begun to develop in some of these 15 days old larvse (PI. VII, 

 Fig. 2), and also the rudiment of the sea-urchin is distinct. 



Echinopluteus of Temnopleurid (?), Species a. 



In a plankton sample from off Jolo, taken the 20th of March 1914, 

 an Echinoid larva was found which agrees in the essential features of its 

 skeletal structure so closely with the Mespilia-lavya, that it can hardly 

 be doubted that it must belong to a related form. It is, of course, impos- 

 sible to ascertain which form this is, and at present no more can be 

 said than that it belongs most probably to one of the numerous Temno- 

 pleurids occurring in these seas. It is very tempting to suggest that it 

 might belong to one of the SaZmacis-species ; but there is no real support, 

 at present, for such suggestion. The larva is, unfortunately, in too 

 poor a state of preservation for giving a whole figure of it; but its main 

 features are distinctly seen, and the skeleton is well preserved ; it presents 

 some very marked features by which the larva may be easily recognized. 



The larva is in beginning metamorphosis; the absorption of the body 



8 



