43 



a basket structure; the postoral rod is fenestrated. The skeleton is only 

 very slightly thorny. 



Beyond this stage I did not succeed in rearing the larvae. No figures 

 can be given, because the "laboratory" conditions at Hilo did not permit 

 any drawing of the living larvae, and the skeleton has been dissolved 

 in the preserved specimens. 



The very conspicuous difference in the skeletal structure between the 

 larvae of this species on one hand (basket-structure and fenestrated rods) 

 and the other Ly/ec/jinus-species on the other hand (no basket-structure, 

 no fenestrated rods) would seem to necessitate the conclusion that 

 the species verruculatus cannot be congeneric with the other 

 Lyfec/iinus-species, but should form a separate genus, in spite of the 

 fact that it seems to afford no very prominent structural differences 

 from those species. 



Toxopneustes pileolus (Lamk.) 



PI. VIII Fig. 8. 



Fertilization of this species was undertaken repeatedly during the 

 months April, May and June 1914 at the Biological Station at Misaki. 

 In no case did I succeed in rearing the larva beyond the 

 first larval stage; evidently it is not very hardy, since 

 other Echinoid larvae (e. g. Heliocidaris tuberculata) were 

 reared to their full shape under quite similar conditions. 



The gastrula stage was reached at about 24 hours 

 age, and at the age of about two days the skeleton 

 had begun to appear and also the first indication of 

 the postoral arms was evident. The shape of the young 

 larva (PI. VIII Fig. 8) is the usual, with a short, trunc- 

 ated body. One of the cultures was kept for about 3 

 weeks, but even at that age the larvae had not yet 

 developed beyond the first stage, the only difference 

 from the younger specimens being that the postoral 

 lobe had become distinctly concave in the middle at 

 the oral edge — an indication that vibratile lobes will 

 be found in this larva. The pigmentation is not very 

 prominent; there are some scattered, red pigment cells 

 and the points of the arms are reddish. The skeleton 

 forms a basket structure (PI. VIII Fig. 8; Fig. 10); both 

 the body rod and the recurrent rod are somewhat 

 thorny. There is a deep sinuation at the point where 

 the body rod and the postoral rod join; the latter is 



Fig. 10. Skeleton of 

 tlie young larva of 



Toxopneustes pi- 

 leolus. Side view; "'"/i. 

 Letters as in fig. 5. 



6* 



