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at that time, they were preserved, no attempt being- made to have them 

 metamorphose completely. Whether the larva will take so long time to 

 develop under better conditions (more food, more congenial temperature?) 

 must be left undecided. 



The first larval stage (PI. XI, Fig. 1) shows the typical form, offering 

 no marked special features. The body is short, the arms rather long. 

 There is a very distinct suboral cavity. Pigment very scarce; a few 

 pigment cells, mainly in the point of the anterolateral arms. The skeleton 



Fig. 24. Skeleton of larva of Heliocidaris tuberculaia; A. of young larva, side view; B. of 

 fully formed larva, front view. "^Vi. Letters as in fig. 20. 



(Fig. 24 A) is very complicate. The body skeleton forms a basket structure, 

 but not in the usual simple way; there are two recurrent rods, so that two 

 large meshes are formed in each side of the body. In the end of the body 

 there are three transverse connecting rods, all strongly thorny along the 

 hind edge; also the body rod and the recurrent rods are rather strongly 

 thorny. The postoral rod is fenestrated, with many thorns along the outer, 

 fewer — sometimes none — along the inner side. 



The fully formed larva (PI. XI, Fig. 2) is provided with four vibratile 

 lobes, but there are no vibratile epaulets. The anal area is somewhat 

 concave. At the anterior edge there is a pair of small ciliated protuber- 

 ances. The vibratile band is arranged along the dorsal side so as to form a 

 pair of small lobes. The arms are fairly long, narrow ; the postero-lateral 



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