52 



small size of the stomach, oesophagus and rectum, the more conspicuous 

 since the body is fairly elongate. The arms are still quite short; the anterior 

 edge of the oral lobe is rather thickened, the preoral vibratile band 

 being not yet very distinctly differentiated. The skeleton is very charact- 

 eristic, the elongated body rods being rather coarsely thorny and ending 

 in two serrated branches^) (Fig. 15); the postoral rod is fenestrated. 

 There is a small recurrent rod, with the end curving forward, and the body 



skeleton accordingly 

 does not assume a 

 basket structure. 



After 8 days the 

 larvae had reached the 

 shape shown in PI. X, 

 Fig. 6. The postero- 



dorsal arms have 

 developed, their rods 

 being fenestrated. All 

 the arms are fairly 

 broad, but somewhat 

 abruptly narrowed to- 

 wards the point. 

 There is a small pro- 

 minence on each side 

 at the anterior end, indicating the place of the future preoral arms, 

 and further there is a characteristic small thickening on the postoral 

 band where it bends out along the postoral arm. Vibratile lobes or 

 epaulets have not yet been formed, and it then remains undecided 

 whether they exist in this larva; judging, however, from the presence of 

 epaulets in the MespiZm-larva as also in the undetermined Temnopleurid 

 larvae described below it can scarcely be doubted that epaulets, but no 

 vibratile lobes, will be found also in this larva. (Cf. the larva from the 

 Gulf of Siam, mentioned below.) There are only scattered pigment cells, 

 no prominent pigment spot in the point of the arms. 



In the skeleton (Fig. 16) there is still only little change. The absorption 

 of the body rods has begun, one of the end branches having disappeared. 



1) In the preliminary notice "On tiie development of some Japanese Echinoderms" p 546 

 It IS stated that the main rod of the body skeleton in the Temnopleurid larva; "has a median 

 process off the posterior end of the stomach, and beyond this process there is a short proloncr- 

 ation, which becomes absorbed in the later stages". While it really has this appearance whe^n 

 seen from the ventral or dorsal side, the side view of the body makes it evident that it is more 

 correct to say that the body rod ends in two branches, one of which (the ventral) may be 

 directed more or le-ss directly downwards; this latter appears to be the first to be absorbed, 

 when the full larval shape is about to be formed. 



Fig. 15. Skeleton of larva of Temnopleurus ioreumaticus, 1st 



stage. A. from the ventral side; B. side view, '""/i- 



Letters as in fig. 5. vtr. ventral transverse rod. 



